Supplementation of ruminants on winter pastures

Supplementation of ruminants on winter pastures

Industry Sector: Cattle and Small Stock

Research focus area: Livestock production with global competitiveness

Research Institute: University of Pretoria

Researcher: Prof Willem.A. van Niekerk PhD (Agric) Animal Science

Research Team:

TitleInitialsSurnameHighest Qualification
ProfLourens. J.ErasmusPhD (Agric) Animal Science
PhD (Agric) Animal Science
MSc (Agric) Animal Science
MrHMynhardtMSc (Agric) Animal Science

Final report approved: 2016

Aims of the project

  • To develop a cost-effective supplementation strategy for ruminants under low quality winter forage conditions
  • To maintain body weight during the wineter season by assessing different sources and levels of nutrients that enhances poor quality roughage utilisation
  • To investigate intake, fiber degradation and microbial protein production when various types and levels of nutrients are supplemented to ruminants kept at maintenance under extensive conditions

Executive Summary

A series of studies was conducted to evaluate differential energy and nitrogen (N) sources as supplemental feed to sheep grazing low quality winter grazing in the High veldt. Knowledge on supplementation under local conditions are limiting as the majority of supplementation studies are funded and performed in the more temperate areas. Results indicated that higher N and energy inclusion levels are necessary to optimize ruminant production under local conditions compared to temperate areas. In addition, the ratio of fermentable energy to available protein is an important parameter in optimizing supplementation programs. It is concluded that the supplementary recommendations from the current feeding tables does not describe the requirements and nutrient quality of the tropical grasses satisfactorily and as such, cannot be used to predict supplementation responses by the tropical forage fed ruminant.  del can be used for further sensitivity analyses and “what if” scenarios as well as a database to answer specific questions.




Every year sheep might lose up to 30% of their summer body weight gain during the dry winter periods in the high veldt.  While these weight losses have an economic impact on its own, it also is associated with an increased susceptibility for diseases and parasitic infestations and decreased reproductive performances. It generally is considered that protein or non-protein nitrogen (NPN) supplementation is necessary to limit these weight losses during these periods. However, due to the type of grass found in the High veldt area of Southern Africa, data is limiting on the effects of supplementation of ruminants grazing these types of grasses (See box: Differences between C4 and C3 grasses). As such, supplementations recommendations derived from current feeding tables seldom satisfy the needs of the grazing ruminant in Southern Africa. Therefore, a series of studies was conducted at the University of Pretoria to determine and quantify the requirements of the ruminant grazing low quality Eragrostis curvula hay commonly found in the Southern Africa High veldt.

* References and correspondence can be obtained from the author:

Box 1: Differences between C4 and C3 Grasses

The acronyms C3 and C4 refer to the first product of the photosynthetic processes in the respective grasses with the first product of photosynthesis in the C3 grass being phosphoglycerate (a 3 carbon structure) while for the C4 plant, the corresponding molecule is a 4 carbon molecule (oxaloacetate). C3 grasses are temperate grasses and are adapted to the temperate regions of the world where rainfall is more constant with maximum temperatures seldom topping 22 OC. In contrast, C4 grasses are more adapted to the subtropical and tropical climates with temperatures frequently topping 25oC during the growth period. These areas also are associated with seasonal droughts and the occasional frost. Due to these extremes in temperatures and seasonal droughts, C4 grasses contain more bundle sheath cells and less available nutrients compared to C3 grasses during all maturity stages. Ruminant production therefore in general is significantly lower in ruminants grazing C4 grasses compared to temperate C3 grasses, especially during the dormant stage of the grass where lignification of the C4 grasses reduces the availability of the nutrients even further. As such, supplementation requirements and responses differ between ruminants grazing these grasses. However, the majority of supplementation studies in the past have been conducted on C3 grasses as it is found more in the European countries where research funding is more available. As such, as more studies conducted on low quality C3 grasses are incorporated in the current feeding tables, supplementation requirements derived from these tables to the low quality tropical forage fed ruminant are not always accurate. As such, the need was established to conduct research through the financial support of the **RMRD-SA on the nutritional requirements of the low quality tropical forage fed ruminant in order to improve ruminant production in Southern Africa.

*RMRD -SA – Red Meat and Research Development, South Africa

Results and Discussion

Forage intake and digestibility was not influenced by either the level of urea or starch supplementation to the wethers. However, CP-balance, measured as CP intake – CP excretion in the faeces and urine, increased from 12.5 g CP/day in the LU wethers up to 70 g CP/day in the EHU wethers. Based on these observations, only the EHU treatment supplied sufficient protein to potentially satisfy the needs of the 50 kg wethers as they require 65 – 70 g CP for maintenance. These recommendations are significantly higher than the recommendations set in the current feeding standards, however, it is in alignment with the observations and recommendations set out by **Leng (1995) studying ruminants grazing tropical grasses in Australia.

Forage intake and digestibility was not influenced by either the level of urea or starch supplementation to the wethers. However, CP-balance, measured as CP intake – CP excretion in the faeces and urine, increased from 12.5 g CP/day in the LU wethers up to 70 g CP/day in the EHU wethers. Based on these observations, only the EHU treatment supplied sufficient protein to potentially satisfy the needs of the 50 kg wethers as they require 65 – 70 g CP for maintenance. These recommendations are significantly higher than the recommendations set in the current feeding standards, however, it is in alignment with the observations and recommendations set out by **Leng (1995) studying ruminants grazing tropical grasses in Australia.


An important parameter in ruminant nutrition is microbial protein synthesis (MPS) as it gives an indication of the efficiency of the rumen microbes. During the dry winter months, MPS generally decreases due to the lack of available nutrients in the roughages (Leng, 1990, 1995) which decreases the productivity of the animal which is experienced as weight loss by the farmer.  In this study, MPS increased almost 50% from 78 g MPS to 106 g MPS as the level of starch supplemented was increased from 200 (LS) to 280 (HS) g starch/day. This observation is in agreement with suggestions made by Leng, (1990; 1995) that energy is an important nutrient driving MPS in the tropical forage fed ruminant, provided that the protein requirements of the ruminant have been met. Interestingly, energy supplementation for the temperate forage fed ruminant is not always advocated as these grasses contain higher concentrations of water soluble carbohydrates compared to the tropical grass.

Based on the above results, higher levels of both protein and energy supplementation is necessary to optimise ruminant production during the dry winter months in the High Veldt. The question now was asked whether there was an “ideal” quantity of protein and energy to be supplemented to ruminants grazing low quality “tropical” forages.

Graph 1 is a schematic representation of MPS per unit CP intake (MNS: N intake) while Graph 2 represents the mean rumen ammonia nitrogen (RAN) concentration as influenced by the ratio of starch supplemented to available protein intake.

Graph 1

Urea supplementation across all three starch treatments affected the MPS: CP ratio similarly with the ratio decreasing from almost 3 to below 1 where the wethers were supplemented with the higher urea treatments (HU and EHU). It is important to note that alleviated MPS: CP levels (above 1) could be indicative of CP deficiency as more microbial protein was synthesized in the rumen compared to dietary CP intake. The additional CP required to produce the microbial protein under these circumstances is derived from body protein catabolism which in itself, is an inefficient process, resulting in an excessive body weight loss. As such, in this trial, it is suggested that the protein intake of the wethers supplemented with at least 26.4 g urea/day (HU) was sufficient to meet the requirements of the wethers.

Graph 2

An inverse relationship was observed between RAN and the ratio of starch: digestible protein intake (Graph 2) with RAN decreasing and plateau between 5 and 10 mg RAN/ dL rumen fluid as the ratio increased. An inflexion point was observed where RAN increased exponentially to levels as high as 25 and even 30 mg RAN/dL rumen fluid as the ratio decreased below 2: 1. This graph highlights the importance of supplementation of both rumen available energy sources (starch in this instance) as the supplementation of only RDP sources to the ruminant could lead to an increased risk of ammonia toxicity under these circumstances.


The results from this study suggest that the supplementation requirements of 50 kg wethers grazing low quality tropical forages (2.7% CP) differs to the current feeding standards as:

  • Higher levels of protein (urea supplementation up to 26.4 g urea per day per wether or 3% urea of the total DM intake) is necessary to optimise CP balance in the tropical forage ruminant.
  • Starch supplementation (up to 280 g/wether/day or almost 20% of the total DM intake) in addition to urea supplementation is necessary as tropical grasses not only are deficient in protein, but also in easy available energy.
  • For wethers grazing low quality tropical grasses, the ideal ratio of starch supplemented to digestible protein intake lies between 2 and 3: 1.
  • Additional research is necessary to study the effects of other energy sources and protein sources on rumen environment and the production parameters of the tropical forage fed ruminant as these sources might have different availabilities compared to urea and pure starch within the rumen.

The authors wish to thank the Red Meat Industry and Research Development (RMRD) for their financial support of this study.

Please contact the Primary Researcher if you need a copy of the comprehensive report of this project –
Willem van Niekerk on

Shiga toxin-producing Escherichia coli in beef

Prevalence and risk factors of Shiga toxin-producing Escherichia coli serotypes in beef at abattoirs and retail outlets in Gauteng

Industry Sector: Cattle and Small Stock

Research focus area: Red Meat Safety, Nutritional Value, Consumerism and Consumer Behaviour

Research Institute: Department of Production Animal Studies, University of Pretoria

Researcher: Prof. Peter Thompson Ph.D.

The Research Team


Year of completion : 2017

Aims of the project

  • To determine the prevalence O157 and non-O157 Shiga-toxin producing Escherichia coli (STEC) in beef abattoirs in Gauteng
  • To determine the prevalence O157 and non-O157 STEC in beef and beef products at retail outlets in Gauteng
  • To identify the important STEC serotypes present in beef and beef products in Gauteng
  • To identify risk factors for STEC contamination of carcasses and beef products in Gauteng

Executive Summary

Shiga toxin-producing Escherichia coli (STEC), particularly the O157 strains, are food-borne zoonotic pathogens of public health importance worldwide. Foods of cattle origin have been implicated in various outbreaks and epidemiological studies have revealed that cattle are major reservoirs of STEC. We conducted cross-sectional surveys from Nov 2015 to Nov 2016, to investigate the prevalence and molecular characteristics of O157 and non-O157 strains of STEC in beef and beef products in the Gauteng province of South Africa.

A total of 265 swab samples of beef carcasses from 12 abattoirs and 399 beef products from 31 retail outlets were screened for STEC using a multiplex PCR. The overall prevalence in abattoir samples was 37% (55/149) in summer and 34% (39/116) in winter. In beef products at retail outlets it was 20% (27/137) in autumn, 14% (18/130) in winter and 17% (22/132) in summer; the highest prevalence was detected in boerewors (35%) followed by mincemeat (21%). The predominant serotypes detected were O113 (19.4%) and O157 (14.9%) in beef products, and O113 (14%) from abattoirs.

Our results demonstrate that STEC is present in South African beef and beef products, and that this may pose a real food-borne disease threat. Further investigation of the epidemiology of the pathogen is required; it is proposed that this take the form of longitudinal studies to investigate the prevalence of shedding of STEC by cattle in the feedlot, following them through to the abattoir to determine factors associated with carcass contamination.

Additional Comments

As this is part of a PhD project, further molecular work is still to be done on the isolates, resulting in further planned publications. The samples also provided material for an MSc student (funded by UP research funds) to work on Salmonella contamination – these results will also be made available to RMRDSA once finalized.

Popular Article

Assessing the prevalence of shiga toxin-producing escherichia coli in beef at abattoirs and retail outlets in gauteng

Dr Lorinda Frylinck, Senior Navorser, LNR-Diere Produksie, Irene.


The production of safe and wholesome beef and beef-derived food products is the highest priority for the beef industry in South Africa. There are potential risks associated with the possible presence of harmful pathogens in the food production chain; however, clear guidelines and regulations have been implemented to reduce these risks to a minimum and ensure a safe product for consumers. Nevertheless it remains important to continually assess these risks and to ensure effective implementation of control measures.

Shiga toxin-producing Escherichia coli (STEC) are bacteria associated with food and waterborne diseases and have been recognized as causing public health problems worldwide. The WHO Foodborne Disease Burden Epidemiology Reference Group (FERG) reported that ‘Foodborne STEC’ caused more than 1 million illnesses and 128 deaths in 2010 (8).

Of the over 470 different serotypes of STEC detected in humans, the O157:H7 serotype is the most frequently associated with large food and water-borne outbreaks (7). However, non-O157 STEC have been increasingly isolated from cases of haemorrhagic colitis (severe GIT infection and bloody diarrhoea) and as well as some fatal kidney failure (HUS; haemolytic uraemic syndrome) cases.

Although the first report of the occurrence of HUS in South Africa dated as far back as 1968 (6), the causative agent was poorly understood at that time. The first clinically proven incidence of E. coli O157:H7 in South Africa was later linked with haemorrhagic colitis (3). The importance of the pathogen in South Africa and other southern African countries has, however, been highlighted by subsequent major outbreaks of bloody diarrhoea in which E. coli O157 strains were implicated (4). Of particular interest was a study in Gauteng province in 2011, in which 7.7% of children with diarrhoea were positive for E. coli O157 (5).

Epidemiological investigations have revealed that cattle are a major reservoir of STEC. Many outbreaks of E. coli O157:H7 have been associated with beef, in particular ground beef, and analyses of some cases have identified undercooked beef as a significant risk factor. However, the fact that E. coli-associated conditions in humans, such as HUS, are not as yet notifiable in South Africa may mean that the occurrence of STEC-associated disease in humans is under-reported. In addition, given the weight of evidence from elsewhere in the world, it is possible that contamination of beef products is also a risk factor in South Africa.

Research problem and objectives

There is a dearth of current information on the frequency of occurrence of O157 and non-O157 strains of STEC, and on the risk they pose to consumers of beef products, in South Africa. Hence, the objective of this study was to determine the prevalence and characteristics of O157 and non-O157 STEC strains in beef carcass and beef products sold at retail outlets in the Gauteng province of South Africa.

Materials and Methods

During a one-year period from Nov 2015 to Nov 2016, two independent cross-sectional surveys were carried out to determine the prevalence of STEC at abattoirs as well as at retail outlets where beef-based food products are sold.

Study 1: Twelve abattoirs (six high throughput and six low throughput) were selected and each was visited during summer and winter months for sample collection. Five animals were randomly selected in each abattoir and tagged for sample collection. Firstly, samples were collected by swabbing the skin of the perineal area immediately after slaughter. Thereafter, carcass swab samples were collected from different parts of the carcass at various stages during processing, including pre-evisceration, post-evisceration, post-washing and 24 hours post-chilling.

Beef carcass sampling and processing at the abattoir

Study 2: A total of 31 retail outlets including both large supermarket chains and smaller butcheries were randomly selected. Visits were made to each of these outlets during autumn, winter and summer months of 2016 for sample collection. Sampling of five types of popular beef products (brisket, boerewors, mince, cold meat, and biltong) was done at each outlet during each visit.

Each sample was analyzed for the presence of Shiga toxin-encoding genes (stx1and stx2) using conventional multiplex PCR. All samples positive for stx genes based on PCR were screened for the following O-serotypes: O26, O91, O103, O111, O113, O145 and O157 using a multiplex PCR assay.

Results and Discussion

Overall, the prevalence of STEC in beef carcass swabs collected from 12 red meat abattoirs across Gauteng province during summer and winter months was 35.5% (94/265). The highest prevalence (50%) was detected in perineal samples, which is hardly a surprise because cattle are an established reservoir of STEC; this may therefore reflect the prevalence of the pathogen in cattle arriving at abattoirs. Transportation stress is known to increase the shedding of enteric pathogens and could therefore be a contributing factor to the observed high prevalence in perineal samples. STEC was found in 39% of both pre-evisceration and post-evisceration carcasses, while washed carcasses and 24 hour chilled carcasses had a lower prevalence of 23% and 20% respectively. Therefore, although washing of carcasses at the abattoir removed much of the STEC contamination, the fact that the bacteria were still present on the surface of some chilled carcasses is of potential food safety significance, since cuts from these carcasses end up for sale in various forms at retail outlets.

Boerewors on display in a retail outlet

Of the 399 beef products sampled from 31 retail outlets, 67 (16.8%) were contaminated by STEC strains, an observation that is of food safety significance if such products were to be improperly cooked and consumed by highly susceptible individuals.

The highest prevalence of STEC was detected in boerewors (35%), followed by minced meat (21%). Ground beef ordinarily includes meat from many carcasses; consequently a few infected livestock could potentially contaminate a great quantity of ground beef. Biltong had the lowest prevalence of contamination (5%), while brisket and cold meat had 11% and 6% respectively. These results are in contrast to a previous study in South Africa, in 2009, involving biltong, cold meat and minced meat at retail outlets, which found that 2.8% of the samples were positive for E. coli O157 (1).

The prevalence of STEC in abattoir and retail outlet samples was somewhat higher during the summer months compared to the winter months. While many factors are believed to affect the prevalence of E. coli O157:H7, only season has been consistently shown to impact the shedding of this bacterium by cattle (2), and some previous studies have also observed a higher prevalence of shedding during the warmer months than the winter months.

The serotype analysis showed that O113 was the post prevalent serotype both on beef carcasses (14%) as well as in beef-based products (19%). This observation is of particular interest considering that O113 is an emerging serotype associated with human illness and sometimes with HUS in several countries including Spain, Belgium and Australia. Serotype O113 of STEC may therefore potentially be important in human diseases in South Africa and this requires further studies. Some of the other serotypes detected  have also previously been implicated in human diseases elsewhere in the world.

Unlike in abattoir samples where the prevalence of serotype O157 was very low (1%), a higher prevalence of 15% was detected in retail meat samples. This finding may be explained in part by the fact that the current study was cross-sectional by design (giving a “snapshot” at a particular point in time) and not a longitudinal study. Therefore serotype O157-contaminated beef products may have originated from abattoirs not sampled in the current study, and the prevalence may vary greatly between places and over time. There is also a possibility that it may partially also be a result of contamination from other sources at the retail outlet level.

Mince meat on display in a retail outlet


This study has shown that contamination of beef products with potentially harmful bacteria can occur during different processing stages. The low numbers of reported cases of food-associated disease in South Africa suggest that the risk to consumers is low; however, it is not known whether all cases are reported, or that all cases are correctly diagnosed. Therefore, further research is needed in order better understand the dynamics of foodborne pathogens in South Africa, to accurately assess the risk they pose, and to accurately inform control measures.

It is well known that efficient implementation of control measures during slaughter and processing procedures can greatly reduce meat surface microbial contamination and ensure the safety of the final product. The South African Meat Safety Act (2000) has addressed potential risk factors by adopting several internationally recognized preventive measures such as the Hazard Analysis Critical Control Point (HACCP) system and Good Manufacturing Practices (GMP) in order to promote safe meat for consumers. The application of GMP and HACCP principles during handling and processing of products, as well as the proper cooking of meat products before consumption, will effectively reduce the threat of food borne disease.


We thank Red Meat Research and Development South Africa (RMRD SA) for funding this research and the Gauteng Department of Agriculture and Rural Development for granting us access and assistance to carry out the cross-sectional survey at the abattoirs.


  1. Abong’o, B.O. and Momba, M.N., 2009. Prevalence and characterization of Escherichia coli O157: H7 isolates from meat and meat products sold in Amathole District, Eastern Cape Province of South Africa. Food Microbiology, 26(2), pp.173-176.
  2. Berry, E.D. and Wells, J.E., 2010. Escherichia coli O157: H7: recent advances in research on occurrence, transmission, and control in cattle and the production environment. Advances in Food and Nutrition Research, 60, pp.67-117.
  3. Browning, N.G., Botha, J.R., Sacho, H. and Moore, P.J., 1990. Escherichia coli O157: H7 haemorrhagic colitis. Report of the first South African case. South African Journal of Surgery, 28(1), pp.28-29.
  4. Effler, E., Isaäcson, M., Arntzen, L., Heenan, R., Canter, P., Barrett, T., Lee, L., Mambo, C., Levine, W., Zaidi, A. and Griffin, P.M., 2001. Factors contributing to the emergence of Escherichia coli O157 in Africa. Emerging Infectious Diseases, 7(5), p.812.
  5. Galane, P.M. and Le Roux, M., 2001. Molecular epidemiology of Escherichia coli isolated from young South African children with diarrhoeal diseases. Journal of Health, Population and Nutrition, 19(1), pp.31-38.
  6. Kiibel, P.J., 1968. The haemolytic-uraemia syndrome: a survey in Southern Africa. South African Medical Journal, 42(27), pp.692-698.
  7. Mora, A., Herrera, A., López, C., Dahbi, G., Mamani, R., Pita, J.M., Alonso, M.P., Llovo, J., Bernárdez, M.I., Blanco, J.E. and Blanco, M., 2011. Characteristics of the Shiga-toxin-producing enteroaggregative Escherichia coli O104: H4 German outbreak strain and of STEC strains isolated in Spain. International Microbiology, 14(3), pp.121-141.
  8. WHO [World Health Organization], 2015. WHO estimates of the global burden of foodborne diseases. Available at

Please contact the Primary Researcher if you need a copy of the comprehensive report of this project – Peter Thompson

Evaluation of methane measuring techniques

Evaluation of different techniques to quantify methane emissions from South African livestock

Industry Sector: Cattle and Small Stock

Research focus area: Sustainable natural resource utilization

Research Institute: University of Pretoria

Researcher: Dr JL Linde du Toit

Title Initials Surname Highest Qualification
Prof WA van Niekerk PhD
Mr J van Wyngaard MSc
Mrs Z Goemans BSc(Agric)

Year of completion : 2018

Aims of the project

  • To measure methane emissions from livestock using the SF6 technique
  • To measure methane emission from livestock using the handheld laser methane detector (LMD) technique
  • To compare the results of the SF6 and the LMD techniques

Executive Summary

The need to verify greenhouse gas inventories demands the development of high throughput, economical yet accurate short-term measurement techniques, such as the laser methane detector (LMD). The aim of this project was to compare methane (CH4) emission rates as measured by the LMD to the sulphur hexafluoride tracer gas (SF6) technique from lactating dairy cows grazing pasture and to evaluate the practicality of the LMD measurement protocol under grazing conditions in the temperate coastal region of South Africa. Methane production was determined from six lactating Jersey cows on pasture using both techniques. The data generated by the LMD had a superior daily repeatability compared to the SF6 technique in the present study. A higher between-cow coefficient of variation (CV) (0.6 vs. 0.4) from the LMD compared to the SF6 technique was observed and this was ascribed to the sensitivity of the LMD to ambient conditions, animal movement while grazing and time of measurement. Methane production as measured by the SF6 technique (348 g/d) was higher (P<0.05) compared with the LMD technique (82.6 g/d).

Results from this study indicated that the LMD yielded approximately a 70% lower average daily CH4 production when compared to the SF6 techniques under the experimental conditions and daily CH4prediction models using the same animals and dry matter intakes. The lack of a third measuring technique and a standardized LMD methodology makes an accurate comparison between techniques and published data difficult. Both the SF6 and the LMD methods are viable methods to evaluate differences between mitigation options, for ranking of animals for selection purposes and to identify differences between dietary treatments. More research is needed before new techniques such as the LMD can be employed to determine absolute CH4 daily emissions which can be up scaled for inventory purposes.

Popular Article

Measuring methane from livestock

Recently, methane has been reported as the most abundant organic trace gas in the atmosphere. The radiative forcing of methane (CH4) is significantly higher than carbon dioxide (CO2) and it is estimated that CH4 has a global warming potential of 28 compared to CO2 with an atmospheric half-life of 12.4 years1. Enteric production of CH4 from ruminant livestock production systems is one of the major sources of agricultural greenhouse gas emissions globally. The relatively short atmospheric half-life of CH4 makes it the main target in livestock greenhouse gas mitigation protocols. Methane is also an important indicator of livestock productivity as it is associated with the conversion of feed into animal product i.e meat, milk or fibre.

Methane is produced in the rumen by methanogenic bacteria as a by-product of the fermentation process. Ruminal fermentation by rumen microbes result in the formation hydrogen (H2). Accumulation of excessive amounts of H2 in the rumen negatively affects the fermentation rate and growth of some microbial consortia which will reduce feed intake and production of animals. Methanogens therefore reduce carbon dioxide (CO2) to methane (CH4) and water (H20) thereby capturing available hydrogen and sustaining a favorable fermentation environment in the rumen2. Methane is exhaled or belched by the animal and accounts for the majority of emissions from ruminants. Methane also is produced in the large intestines of ruminants and is expelled in much smaller volumes compared to ruminal methane.

There are a variety of factors that affect CH4 production in ruminant animals, such as: the physical and chemical characteristics of the feed, the feeding level and schedule, the use of feed additives to promote production efficiency, and the activity and health of the animal1. Reductions in greenhouse gas emissions from livestock can be achieved through a range of CH4 mitigation strategies and more efficient livestock production systems through improved genetics and management.

Regardless of the mitigation strategy imposed, any reduction in enteric methane production must be quantified and for this to be achieved, accurate baseline emissions data are essential1. There are currently many techniques available to researchers to quantify CHemissions from livestock each with specific applications and challenges. These techniques vary from tracer and capsules for individual ruminants to whole farm systems. The development of baseline emission data can also be achieved through modeling, employing specific livestock and environmental activity data to estimate emissions. One of the main challenges of the majority of the measurement techniques is the lack of “real time” emissions from grazing ruminants under natural conditions. There is a need to develop measuring techniques and methods which can be standardized, is relatively low-cost and which can deliver reliable, feasible and repeatable assessments of emissions from grazing livestock.

The Sulphur hexafluoride (SF6) technique and spot sampling lasers are two of the techniques which shows promise to measure CHemission from grazing livestock. Researchers recently compared these two techniques in a pasture dairy production system in the Western Cape province of South Africa. It was found that the spot sampling with the laser could be useful for purposes such as selective animal breeding and comparing between different mitigation strategies, where the requirement is for relative emission data but not necessarily daily methane production. This trial highlighted the need to develop specific operational standards when employing methane quantification techniques under natural conditions in order to minimize variation and environmental interference when recording measurements.

Strategies to reduce greenhouse gas emissions and to increase farm productivity are likely to remain vague, random and possibly inefficient without the development of standardized, accurate and reliable CH4 measurement techniques1.


  1. Hill, J., McSweeney, C., Wight, A.G., Bishop-Hurley, G. and Kalantar-zadeh, K., 2016. Measuring methane production from ruminants. Trends in Biotechnology, Vol. 36 (1).
  2. Goopy, J., Chang, C. and Tomkins, N., 2016. A Comparison of Methodologies for Measuring Methane Emissions from Ruminants. In: Methods for Measuring Greenhouse Gas Balances and Evaluating Mitigation Options in Smallholder Agriculture. Editors: Todd S. Rosenstock, Mariana C. Rufi no Klaus Butterbach-Bahl, and Eva Wollenberg Meryl Richards. Springer International Publishing AG Switzerland.
Please contact the Primary Researcher if you need a copy of the comprehensive report of this project – Linde du Toit on

Methane and nitrous oxide from beef cattle manure

Direct manure methane and nitrous oxide emissions from a commercial beef feedlot in South Africa.

Industry Sector: Cattle and Small Stock

Research focus area: Sustainable natural resource utilization

Research Institute: University of Pretoria

Researcher: Dr JL Linde du Toit

Title Initials Surname Highest Qualification
Prof WA van Niekerk PhD
Miss K Lynch BSc(Agric)
Dr L Stevens PhD

Year of completion : 2018

Aims of the project

  • To identify the on-farm manure management system employed in a typical commercial beef feedlot in South Africa
  • To determine the methane emissions from manure in a commercial beef feedlot
  • To determine the nitrous oxide emissions from manure in a commercial beef feedlot

Executive Summary

Methane and nitrous oxide emission from pen surfaces in a commercial beef feedlot in South Africa

Global warming has become a worldwide concern in recent years.  The release of Greenhouse gasses (GHGs) have brought about rapidly changing climate conditions the world over, GHGs produced by various industry sectors are being investigated, researched and laws put in place to limit the production of GHGs wherever possible.  This includes the agricultural sector where extensive animal husbandry has increased the global carbon footprint and environmental pollution.

The International Panel of Climate Control (2006) has three Tiers that estimates methane (CH4) values, one of the main GHGs, from the use of default values to the use of more complicated models and experimental data to improve the accuracy of reporting.  This study investigated the contribution of manure GHGs emissions to livestock emissions focussing on intensive beef feedlot manure emissions. At present in South Africa, these values are only roughly estimated and are only available on an IPCC Tier 2 level.  Gaseous emissions from livestock waste, specifically beef cattle waste, are affected by a variety of external factors (atmospheric temperature, humidity, soil conditions, ration consumption and manure management practices) as well as internal factors, (ration digestibility, nutrient absorption and gut health).

The objective of the study was to achieve an understanding of the gaseous emissions, specifically methane (CH4) and nitrous oxide (N2O), from beef cattle feedlot pen surfaces from a commercial beef feedlot in South Africa as influenced by diet and season, using the closed chamber method of gas collection over the three prominent seasons experienced in Mpumalanga, South Africa.  The sampling of these various factors would lead to more accurate reporting, conforming to Tier 3 methodology results.

Random pen surface and emissions samples were taken from three pens per each feedlot ration fed. The results indicated significant differences in soil/manure characteristics, but little effect on ultimate CH4 and N2O emissions from the pen surface were found across treatments. Similar results were observed for the rangeland manure analysed and manure emissions from manure management practices at the feedlot.  Ambient temperature had a tendency (p<0.10) to affect CH4 and N2O emissions with higher temperatures resulting in higher emissions but. Overall soil and manure characteristics were affected by diet treatments and seasonal variation.  It must be noted that the lack of significant differences in gas emissions in the present study could have been due to sampling error. The gas emissions observed did show a trend between treatment levels and manure management practices within the feedlot, with the effluent dams and manure piles recording the highest CH4 emissions over each of the measured seasons.  The CH4 emissions varied between seasons within the feedlot, rangeland and manure management practices, but a level of significance was never observed even though manure characteristics observed significant differences.  The N2O emissions observed no set trend between areas measured on the feedlot.  The varying values, and negative values obtained may indicate sample error, or a general uptake of N by soil or microorganisms (Chantigny et al., 2007; Li et al., 2011).

In conclusion, it was found that manure characteristics are affected by season and diet characteristics which tended to have an effect on the rate of CH4 and N2O emissions from the manure, although not significantly.

Popular Article

Feedlot greenhouse gas study analyses emissions from pen surfaces and manure management

By CJL du Toit

Researchers from the University of Pretoria spend time at a commercial beef feedlot in Mpumalanga, South Africa to gain a better understanding of the greenhouse gas emissions originating from feedlots pen surfaces and manure.

Why are GHG emissions important to agriculture?

In agriculture and livestock production systems the three main greenhouse gases (GHG) include methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2).  Greenhouse gases impact the environment through their ability to trap heat which depends on their capacity to absorb and re-emit infrared radiation and the atmospheric life time of the different gasses.  Increasing atmospheric concentrations of GHG caused by fossil fuel combustion, industrial activities, land use change and agricultural activities contributes to changes in global temperatures and rainfall patterns which could impact directly on agricultural and livestock production.

Accurate estimation of GHG from anthropogenic sources is an increasing concern given the current and potential future reporting requirements for GHG emissions.  Research measuring GHG emission fluxes from feedlot surfaces and manure management has been very limited and this was the first research project on the topic under South African conditions.

Livestock manure and GHG emissions

Livestock manure is a source of nutrients and can be used for various purposes including soil amendments to improve fertility and productivity and the generation of green energy.  The main GHG emitted by manure are CH4 and N2O. Methane is produced during anaerobic decomposition of organic matter and N2O is emitted during nitrification and de-nitrification processes. Feedlot manure GHG emissions is influenced by a variety of factors including manure management (pile, anaerobic lagoon, rangeland), manure application (fertilization of rangeland, composting, bio-fermentation), temperature, aeration, moisture and the sources of nutrients in the manure which is in part caused feed inefficiencies. Emission is also influenced by animal factors in the feedlot such as stocking density which will influence the amount of manure deposited, feed intake and digestibility, animal type and age.

What did the researchers do?

Following an extensive review of current literature on GHG emission flux quantification from pasture, cropping and livestock enterprises it was decided to adopt closed static chambers as the measurement methodology. The aim of the study was to determine the effect of feedlot ration and season on the GHG emissions from manure at different sites within in a commercial feedlot operation. Chamber bases were randomly installed at each manure management site (rangeland, pen surface, manure piles and water catchment lagoons) during each season. The seasons were classified as wet and hot (WH), dry and cold (DC) and dry and hot (DH).

Gas samples were drawn from the chambers during mid-day at four time intervals within a 40 min measuring period and analysed using a gas chromatograph to determine average CH4 and N2O fluxes.

What did the researchers learn?

The method employed resulted in large variation within results sets mainly due to difficulty in sealing the chambers bases especially in the pen surfaces which were extremely compacted. The random placement of chambers also caused variation in results as some chambers had a higher manure density and factors such as soil and manure moisture varied between different locations within each pen.  The results yielded an average pen surface manure CH4 emission factor of 449 g/head/year which was 50% lower compared to feedlot manure emission factors previously calculated of 870 g/head/year using IPCC (2006) based models.  The N2O emissions measured from pen surfaces (10.95 g/head/year) were much lower than previously calculated or reported emission factors in literature varying from 54.8 to 2555 g N2O/ head/year.  Within the whole manure management system on the feedlot CH4 emissions from the water catchment dams were the highest followed by manure piles, feedlot pen surfaces and manure deposited on rangeland.  Although no statistical differences were found between the different seasons the wet and hot season produced the highest overall CH4 emissions and the dry and cold season produced the highest N2O emission across all manure management sites.

Managing GHG emissions from manure

The mitigation of GHG emissions from manure management in livestock operations is the topic of many research projects globally. Identified mitigation strategies are already being used by producers but new techniques and fine-tuning of existing options will lead to new and improved alternatives which can be tailored to country or regions specific production systems. The mitigation of GHG emissions from livestock production systems can be complicated as a strategy that reduces one emission may increase the other. Manure emissions can be reduced through two main actions namely input (providing of organic matter e.g. feeds) and manure management.  Overfeeding of nutrients such as nitrogen (N) will result in an increase in the amount of N excreted in manure which will lead to increased N2O emissions. To reduce GHG emission from manure producers will have to use feeding regimes that will maximise feed efficiency and reduce nutrient wastage. The management of on-farm manure can also be tailored to reduce GHG emissions and the effect of production systems on the environment.  The time of manure application to soil and rangeland is important to reduce emissions. Producers should avoid spreading manure when soil is are wet as this will increase CH4 emissions and attempt to reduce the storage time of manure on the farm. The use of technologies such as covered lagoons, digesters, aeration of manure and composting has all been employed to reduce CH4 emissions from manure.

On-going research

There is a need to develop standardised research methodology protocols, for both on-farm and laboratory experiments, which will make it possible to compare mitigation strategies and research results between different studies. Researchers are also attempting to understand the interplay of CH4 and N2O as it seems that the processes that produce these GHG are related.

Please contact the Primary Researcher if you need a copy of the comprehensive report of this project – Linde du Toit on

Chilling and electrical stimulation of beef carcasses

Effects of chilling and electrical stimulation on carcass and meat quality attributes of selected breeds of cattle with different carcass weights

Industry Sector: Cattle and Small Stock

Research Focus Area: Animal Products, Quality and Value-adding

Research Institute: University of Pretoria

Researcher: Prof Edward Webb

Title Initials Surname Highest Qualification
Mr Babatunde Agbeniga MSc
Dr P.E. Strydom PhD

Year of completion : 2018

Aims Of The Project

  • To compile a comprehensive literature review on current chilling and electrical stimulation guidelines
  • To compare chilling and electrical stimulation of selected cattle breeds of different carcass weights and to evaluate the effects of different chilling regimes and different stimulation procedures on carcass and meat quality attributes
  • To make recommendations to the meat industry on acceptable ways of chilling and stimulating carcasses in order to obtain the best quality carcasses and meat

Executive Summary

This research focused on acceptable ways of chilling and electrically stimulating beef carcasses in order to obtain the best quality meat, given the current use of growth enhancing molecules (beta-adrenergic agonists) and the current increase in carcasses size to curve the negative impact of escalating maize prices on the economics of intensive feed of beef cattle.

The literature survey suggest that low voltage electrical stimulation (LVES) is safer and more practical in South African abattoirs compared to high voltage electrical stimulation (HVES). The current research indicates that low voltage electrical stimulation has beneficial effects on meat quality of beef carcasses. Furthermore, early post mortem LVES is more beneficial compared to LVES after evisceration in terms of most meat quality attributes. Shorter duration LVES (30 sec.) was more beneficial compared to long duration LVES (60 sec.). Current chilling regimes of larger carcasses demonstrate that the effects of beta-agonist treatment on beef tenderness becomes negligible with increasing carcass size, provided that such carcasses are electrically stimulated early post mortem. Optimum carcass stimulation and chilling regimes were proposed for commercial beef abattoirs in South Africa.


Scientific publications (ISI peer reviewed)

  1. Agbeniga, B. & Webb, E.C. (2018). Influence of carcass weight on meat quality of commercial feedlot steers with similar feedlot, slaughter and post-mortem management, Food Research International, 105,793-800. (IF=3,086)
  2. Agbeniga, B. & Webb, E.C. (2018). Effects of timing and duration of low voltage electrical stimulation on selected meat quality characteristics of light and heavy bovine carcasses, Animal Production Science, (Accepted with minor changes).

Scientific conferences

  1.  B. Agbeniga, E.C. Webb, P.E. Strydom & L Frylinck, 2016. Effects of low voltage electrical stimulation and carcass size on meat tenderness and drip loss of beef carcasses treated with Zilmax®, 49th SASAS Congress, Cape Town, (Oral presentation).
  2. B. Agbeniga & E.C. Webb, 2015. Effects of duration of electrical stimulation and carcass weight on carcass pH, temperature profile and shear force of Zilmax treated beef carcasses, 48th SASAS congress, Zululand, (Oral Presentation).

Industry lectures

  1. Webb, E.C. (2016) Growth enhancers, residues and beef quality, Red Meat Abattoir Association Conference, Spier, Western Cape,
  2. Webb, E.C. (2016) Abattoir management and carcass and beef quality, Devon abattoir workshop, Protea Hotel, 22 July 2016.
  3. Webb, E.C. (2015). Factors that affect beef carcass and meat quality, North West RPO Koopmansfontein,  October 2015.
  1. Webb, E.C. (2015).Growth efficiency in feedlot cattle, Cattleman’s conference, South African Feedlot Association, March, Kiewietskroon.

Popular Article

Interactions between early and delayed electrical stimulation and carcass size on pH, temperature decline and instrumental shear force of meat samples from Zilmax treated cattle


The time of application and duration of electrical stimulation (ES) on light and heavy carcasses from Zilmax treated animals, poses new challenges in the meat processing industry in South Africa. Owing to the use of Zilmax, larger carcasses are now being processed at abattoirs that were built to accommodate smaller carcasses. This poses new challenges in terms of optimization of conversion of muscle to meat using ES and appropriate chilling regime. In this study, the effects of early or delayed low voltage electrical stimulation (LVES) (110V) applied to light and heavy carcasses of Zilmax treated cattle were evaluated for pH and temperature decline, and the resultant effects on instrumental shear force. One hundred and forty-nine Zilmax treated cattle (mainly steers) were assigned to 10 different treatment groups according to the combination of their carcass weight (≤ 130 or ≥ 145kg side), time of stimulation (early stimulation-3 min post mortem [p.m.] or late stimulation-45 min p.m.), and the duration of stimulation (30 or 60 sec). Analysis revealed significantly (p < 0.05) faster pH decline and the lowest pH in carcasses stimulated before evisceration, at all times of measurement compared to carcasses stimulated late or non-stimulated controls. The time of ES application exerted the greatest influence on the pH profile while duration of stimulation showed minor influence. Heavy carcasses in the early stimulated groups had the lowest rigor- and ultimate pH. Regarding temperature decline, heavy carcasses had the slowest decline (p < 0.05) and the highest carcass temperatures at all times from 45 min to 24 hr p.m. Time of ES application and duration of ES did not affect carcass temperature. In terms of shear force, carcasses stimulated at 3 min p.m. had the lowest (p < 0.05) shear force at 3 and 14 days p.m. compared to carcasses stimulated at 45 min p.m. and controls respectively. Heavy carcass groups, stimulated early, with the lowest rigor and pHu, had the lowest shear force at 3 and 14 days p.m.

Effects of electrical stimulation and chilling on beef quality

Results of our recent study indicates that the time of application of electrical stimulation has an important influence on carcass pH and temperature profile, and in combination with carcass weight, has a large influence on the tenderness of beef. LVES provides a practical way to manipulate glycolysis in order to improve beef tenderness, but it appears that this treatment should be applied early post mortem in ordser to be efficient. Although there has been some suggestions to apply LVES later, the present results show that early post mortem application of LVES produced the lowest shear force, mainly due faster pH decline in combination with high initial carcass temperature.

Previous research suggested that at high muscle temperature combined with low pH, heat shortening may occur, leading to lower beef tenderness. Our results indicate that LVES treatment early post mortem passed through the heat shortening window (above 350C) within 2 hr p.m. when the pH was less than 6. This finding clearly demonstrates that the proteolytic activity was not exhausted by the low pH and elevated initial temperature in the early stimulated carcasses.

Carcass weight also played a part in improving tenderness in the early stimulated carcasses. In addition, Zilmax is known to reduce tenderness in meat but the application of ES could improve tenderness by the early activation of the calpain system. It is important to note that ES-treatment improve but do not completely overcome the negative effects of Zilmax on tenderness. In this study, we found that the combination of early ES and carcass weight significantly lowered the shear force in the heavy carcass groups. Research by Webb and Morris on Zilmax treated cattle also show that heavier carcasses from zilmax treated cattle produced more tender meat.

On the other hand, carcasses stimulated late and the controls had slower pH decline at all times of measurement, which was also reflected in lower tenderness scores at both day 3 and 14 post mortem.

Results on the duration of electrical stimulation indicates that 30 seconds or less (15 seconds) provide most beneficial results, which agrees with a number of other international studies.


It is concluded that the application of low voltage electrical stimulation early p.m (3 min p.m) brought about a significantly (p < 0.05) lower shear force in carcasses from Zilmax treated cattle compared to the ones stimulated late (45 min p.m) and the un-stimulated controls. Heavy carcasses (≥ 145kg) from the early stimulated groups had the lowest shear force values at 3 and 14 days p.m despite passing through the heat shortening window, which was due to lower initial pH and higher initial muscle temperature. More proteolytic activity in the heavy carcass groups was suspected to have contributed to the low shear force values and although, slightly higher (at 5.6 and 5.9 kg) when considering a threshold of 4.9 (Shorthose et al., 1986). It is acceptable, considering the fact that the animals were treated with Zilmax which is known to reduce tenderness.

Please contact the Primary Researcher if you need a copy of the comprehensive report of this project – Prof Edward Webb on

Effects of growth enhancers on residues in lamb

The effects of steroidal growth implants and β- adrenergic agonist, alone, or in combination on feedlot performance and residues in lamb

Industry Sector: Cattle and Small Stock

Research Focus Area: Animal Products, Quality and Value-adding

Research Institute: University of Pretoria

Researcher: Prof Edward Webb

Title Initials Surname Highest Qualification
Dr A.L. Le Riche BVSc, MScAgric
Dr Shaun Morris BVSc(Hons), MScAgric

Year of completion : 2018

Aims Of The Project

  • To investigate the feedlot performance of feedlot lambs treated with different steroidal growth implants, alone or in combination with oral beta-agonist supplementation
  • To investigate the effects of different steroidal growth implants, alone or in combination with oral beta-agonist supplementation on the residues in the meat
  • To investigate the effects of different steroidal growth implants, alone or in combination with oral beta-agonist supplementation on carcass and meat quality

Executive Summary

The objective of this study was to compare four commonly used growth promotants in a commercial sheep feedlot. The steroidal growth promotants chosen for this trial were Ralgro (zeranol), Revalor G (Rev G; TBA/oestrogen- 17β), Revalor H (Rev H; TBA/oestrogen- 17β) and Zilmax® (zilpaterol hydrochloride). The growth promotants were compared with one another and within three sex groups, namely ewe, ram and wether (castrates), to determine which molecule or combination of molecules, if any, had the most benefit and profitability when measured against a control group.  Sheep were stratified based on initial weights and then randomly allocated to treatment groups in a completely randomised control study. All sheep originated from the same farm, and they were of  similar age, breed,  transport method,  processing method, feed ( the only difference being  the groups receiving Zilmax® during the last 18 days of feeding, making provision for 3 days withdrawal), weather conditions, housing and time on feed. A time constant termination date was used in this study, in order to measure the performance of lambs in treatment groups over time.

The experimental groups were compared over a 10 weeks feeding period according to growth and carcass parameters. The parameters that were measured were gain, FI (feed intake), FCR (feed conversion ratio), ADG (average daily gain), WCM (warm carcass mass), DP (dressing percentage), CL (carcass length) and CC (carcass compactness). Data was recorded in an Excel spread sheet and checked for accuracy. The effect of experimental treatments on growth and production parameters were analysed by means of the GLM ANOVA procedure in SAS (2006). Differences between treatment means were tested at the P<0,05 level of significance by means of the Bonferroni multiple range test in order to correct for unbalanced data (missing values). Correlations between variables were analysed by means of the Pearson product moment procedure in SAS.

Data was analysed within weeks, treatment phases and also over the entire experimental period. Effects of sex, steroid treatment and beta-agonist treatment and interaction effects were calculated. In terms of growth and slaughter parameters the use of zilpaterol hydrochloride alone proved most effective. The latter can be explained by the repartitioning effect of the BAR which increased protein accretion as a result. Benefits gained were not always statistically significant, however taking cost of treatment into account, there is a definite financial significance when choosing which combination of growth promotants to use. Muscle and liver samples were collected for residue analyses, which indicated no significant residue’s in any of the treatment groups. The current data indicate that the use of the various combinations of growth enhancing molecules in sheep pose no risk to consumers in terms of the presence of residue’s, provided that the molecules are used according to prescribed procedures and dosages.

Popular Article

In South-Africa, the finishing of cattle in a feedlot, has, over many years, become part of the value chain of marketing beef. Huge amounts of money have been made available for research to find the most cost-effective ways of producing high-quality beef (Le Riche, 2014). Relatively little research in intensive, sheep production for South-African conditions has been done up to now, leaving a number of questions regarding the safe use of certain growth-promoting agents.

Traditionally sheep were finished extensively on the veld as this was thought to be the least expensive option. Alternatively, farmers bought in lambs from others who did not have enough grazing and finished them on harvested corn fields. This is also an inexpensive option as the corn residues are readily available after harvesting. These practises, however, give rise to seasonable availability of lambs with resultant huge fluctuations in lamb meat prices. Furthermore, the national sheep herd has decreased significantly over the last decade. There are various reasons for this. Drought and the resulting reduction in grazing, being one, and the substantial stock losses due to theft and predators, to name but two, being another (Mokolo, 2011).

Whenever a product is in short supply its price escalates. As a result of this, lamb has become an expensive. There, however, remains a HUGE demand for lamb as it constitutes a major source of protein for a significant part of South-Africa’s population. The constant production of lamb, that meets market specifications has thus become more and more important (Buttry & Dawson, 1990).  In an effort to make lamb more readily and constantly available and also more affordable, lamb feedlotting is increasingly being used as a method for increasing the amount of meat being produced. Due to the current high cost of feed and the labour intensive nature of such ventures, the profit margin of a sheep feedlot can be very small.

At the present time it costs about R 326.00 to FINISH a lamb that is market ready within 70 days, (cost of the lamb excluded) (Le Riche, 2014). The total profit made on such a lamb after all production costs have been deducted could be as little as R24 – 00. The profit margin is dependent on the meat: feed price ratio. In an article by Voermol Feeds (2010) it is stated that feed conversion ratio is considered to be the critical aspect of feedlot profitability. Any reduction in feed intake or increase in feed efficiency, without compromising carcass quality, is economically important (Snowder & Van Vleck, 2003)  Thus the lamb that converts feed the best (in other words the lamb that produces the most kilograms of meat, per kilogram of feed consumed), is the most profitable lamb. One could say that , an increase in profits constitutes a decrease in input cost and/or an increase in production output. Cost of feed is an important input cost, whilst growth rate and carcass composition is an important production output (Buttry & Dawson, 1990; Snowder & Van Vleck, 2003).

There is a need to balance more efficient food production, with positive public perception. This has become a great challenge. Professionals in the industry have to determine which products and methods could be optimally used to the benefit of the producers, without gaining negative opinions from the public sector and it  has to go hand in hand with maintaining a high level of consumer safety (Buttry & Dawson, 1990).

Optimal feeding conditions that promote high voluntary intake, added to a high quality, properly balanced ration should promote profitability. The high cost of quality feed is, however, making it even more important to research the responsible, effective use of different types of growth promoting agents, alone or in combination. These products have the potential to:  1) produce animals with a higher meat: fat ratio; 2) to keep the feeding time down to a minimum and to thus reduce the impact on the environment; 3) to increase the ability to supply the protein needs of an ever-growing population.

The use of BAR agonists in ruminant production animals as a growth ENHANCER has been the subject of many heated debates and much media publicity. The reason for this is the very real potential that some of these products, clenbuterol, to name one, can have serious toxic effects in human consumers. (Stachel et al., 2003). BAR agonists used as growth promoting agents, work on the basis that they reduce body fat whilst increasing muscle hypertrophy, without causing significant alterations in organ and bone mass. They are therefore also known as repartitioning agents (Beermann, 2002). Repartitioning literally means the channelling of energy away from storage cells in the liver and adipose tissue towards muscle tissue. The sensitivity of liver and adipose tissue towards insulin is lessened whilst it is increased in muscle tissue (Beermann, 2002).

Their pharmacological action leads to an improved ADG, improved gain efficiency (G: F) and increased hot carcass weight in both feedlot beef and lambs (Reeds, 1991; Beermann, 2002; Estrada-Angulo, et al., 2008). This effect is seen with no SUBSTANTIAL increase in daily DMI.

When age comparison studies were carried out, maturity of muscle tissues proved to be a critical factor with regards to efficacy .It would then make sense that receptor presence and availability would be important in the physiological effect of this drug as mature muscle would have a higher density of receptors available (Beerman, 2002). The lack of response or reduced response in young animals would also act as proof that young muscle fibres lack enough Beta adrenergic receptors, according to Beerman, (2002).

BAR agonists, such as Zilmax® function by stimulating mainly β2- AR. This causes muscle hypertrophy and hyperplasia, lipolysis and reduced lypogenesis as well as the indirect effect of lowered insulin sensitivity. According to Baxa (2010), it does have beneficial effects to treat animals with anabolic steroid implants first, following with the oral application of ZH. Cattle that received this combination treatment showed additive improvements to lean carcass mass and performance, such as ADG and FCR.

Growth enhancers such as hormonal implants and repartitioning agents such as zilpaterol hydrochloride  are used in intensive production systems to reduce the cost of production by decreasing the feeding time, improving feed conversion and increasing the carcass slaughter weight (Pritchard, 1998; Duckett & Andrae, 2001).This should prove to be true for both cattle and sheep feedlots. According to Casey (1998) the efficacy of β- receptor agonists are determined by the relationship between the chemical structure of the compound, the theoretical number of receptors that need to be stimulated to elicit a response and the resultant effect when the β2 receptors are stimulated.


In sheep the best reaction is obtained when Zilmax® is fed during the last 18 – 25 days (usually 21 days) of finishing, leaving time for a three day withdrawal period before slaughter. Previous studies indicate that a minimum of 48 hours was necessary in cattle, to reach a minimal residual level. It can be expected that sheep would generally react in the same manner. At present, the acceptable dosage for ruminants is 0.15 mg/kg/day which cconstitutesa dosage of 70 g/ ton of feed in sheep.

Please contact the Primary Researcher if you need a copy of the comprehensive report of this project – Prof Edward Webb on

Nutrient content of lamb and mutton offal

The nutritional composition of South African lamb and mutton offal

Industry Sector: Cattle and Small Stock

Research focus area: Red Meat Safety, Nutritional Value, Consumerism and Consumer Behaviour

Research Institute: University of Pretoria

Researcher: Dr B Pretorius

Title Initials Surname Highest Qualificaion
Prof HC Schönfeldt PhD
Ms C Muller MSc
Dr N Hall PhD
Ms M Bester MSc
Ms D Human Matric

Year of completion : 2018

Aims of the project

  • To determine the nutritional composition of South African lamb and mutton offal products (raw and cooked)
  • To determine yield, retention and physical composition of the different cooked offal products to ultimately determine the edible portion of each product
  • To incorporate the nutritional composition data and physical composition data into the national food composition tables as well as the food quantities manual of the Medical Research Council

Executive Summary

Offal, also called variety meats, or organ meats or the ”fifth quarter”, have been overlooked in the past in dietary guidelines and recommendations, irrespective of their potential contribution to food and nutrition security. This study focussed on understanding the physical and nutrient composition, as well as the potential nutritional contribution of lamb and mutton offal, when used in the correct amounts, to South African diets.

Significant amounts of protein, iron and zinc (three nutrients of concern in South Africa) can be found in selected organ meats which compared favourably with beef and lamb muscle meat cuts. The most significant findings of the study were the high levels of protein (>10g/100g) found in all cooked lamb and sheep offal cuts ranging from 14.26g/g (cooked lamb intestines) to 32.6g/100g (cooked sheep kidneys). High levels of total iron were found in cooked sheep lungs (TFe=10.73mg/100g); cooked sheep spleen (TFe=11.71mg/100g); cooked sheep liver (TFe=7.95mg/100g) cooked lamb lungs (TFe=8.368mg/100g) and lamb spleen (TFe=22.83mg/100g).

Instead of simply focussing on total protein, attention has shifted to the greater importance of protein quality than actual quantity, emphasising the presence of individual amino acids in a food. Protein quality answers two important questions namely, how much protein as well as what kind of protein should be consumed. Dietary proteins are classified as either being complete or incomplete. Foods containing all essential amino acids (indispensable amino acids) are referred to as a complete protein. The sum of the essential amino acids for lamb and mutton offal varies between 4.2 g/100g and 8.1 g/100g for mutton tongue and liver respectively. The study found that South African lamb and mutton offal adheres to the requirements as set out by the Department of Health to be labelled and proclaimed as a complete, quality protein.

Offal products contribute consistently to the diet not only in terms of essential fatty acids such as linoleic acid (C18:2n-6) and arachidonic acid (C20:4 n-6), but also eicosanoic (arachidic) acid (C20) and docosanoic acid (C22) polyunsaturated fatty acids. Ruminant meats and oily fish are the only significant sources of preformed and C22 PUFA in the diet (Enser, et al., 1998; Wyness, et al., 2011). Although human beings have the metabolic capacity to synthesize C20 and C22 fatty acids from the n-6 or n-3 precursors of linoleic and α-linolenic acid respectively, an increase in the consumption of C20 and C22 n-3 polyunsaturated fatty acids could overcome the perceived imbalance in the ratio of n-6:n-3 polyunsaturated fatty acids in modern diets.

Based on the results of this study South African lamb and mutton offal cuts can be considered a good source of protein and also a nutrient dense food source. Due to the current state of nutrition in South Africa such foods are important commodities and the promotion thereof should be prioritised.

Popular Article

Nutrient density lamb and mutton offal

1Pretorius, B., 1,2Schönfeldt, H.C. and 1Bester, M.

1Department of Animal and Wildlife Sciences, Institute of Food, Nutrition and Well-being. University of Pretoria. South Africa

2Professor and Director: ARUA Centre of Excellence: Food Security

Despite economic growth, undernutrition and food insecurity remain today at unacceptably high levels, while at the same time, diet-related non-communicable diseases (cardiovascular diseases, diabetes and hypertension) have exponentially increased to become the leading cause of mortality worldwide. The situation is set to worsen dramatically in the near future as powerful drivers of change such as population growth, climate change and urbanization converge on food systems. Consumption recommendations for high quality nutrient dense foods such as animal source foods (ASFs) are of utmost importance and should be adhered to, to keep up with the specific physiological demands of each life stage. However it was found that the feasibility for nutritionally vulnerable individuals in South Africa to adhere to these recommendations seems unlikely. The dire economic climate which South Africans, particularly those of low socio economic status, currently have to face, is probably the main reason for the problem that nutritionally vulnerable individuals cannot meet the recommendations of the Food-based Dietary Guidelines for South Africans.

Offal has been overlooked in the past in dietary guidelines and recommendations, irrespective of their potential contribution to food and nutrition security in South Africa. Limited information is available on the composition of South African lamb and mutton organ meats as cooked and consumed at home. This study focussed on understanding the physical and nutrient composition, as well as the potential nutritional contribution of lamb and mutton offal, when used in the correct amounts, to South African diets.

Table 1: Moisture, fat and protein content of 100g edible portion cooked lamb & mutton offal

Lamb Mutton
n=3 Moisture Protein Fat Moisture Protein Fat
  g/100g g/100g g/100g g/100g g/100g g/100g
Intestines 55.2cd 14.3d 31.2a 48.2d 15.3d 37.9a
Lungs 74.1a 21.1bc 6.53b 71.1a 23.2bc 3.97d
Hearts 65.1b 19.3cd 13.5b 57.6bc 20.4cd 20.2c
Livers 61.2bc 23.6bc 8.39b 64.5ab 23.1bc 6.27d
Stomachs 49.6d 24.8ab 29.9a 53.1cd 17.8d 27.3bc
Kidneys 65.8b 24.4abc 12.1b 57.2bcd 32.7a 7.77e
Spleen 67.1ab 29.5a 6.62b 66.2ab 27.8ab 5.23e
Tongues 63.7b 19.2cd 16.8b 52.6cd 15.8d 33.2ab
P-value <0.001 <0.001 <0.001 <0.001 <0.001 <0.001

Note: Means with different superscripts in a column differ significantly

Table 2: Mineral content of 100g edible portion cooked lamb offal

Ca P Mg Cu Fe Zn K Na
n=3 mg/100g mg/100g mg/100g mg/100g mg/100g mg/100g mg/100g mg/100g
Intestines 18.6b 124e 21.9a 0.28b 1.40c 2.60c 75.1d 38.4f
Lungs 8.90b 271c 22.2a 0.46b 8.37b 2.59c 298b 160b
Hearts 5.12b 195d 29.0a 0.49b 3.84bc 2.49c 261b 101cd
Livers 5.03b 423a 28.3a 17.9a 6.07bc 4.17a 315b 70.8e
Stomachs 52.7a 170de 25.3a 0.40b 4.85bc 3.90a 155c 79.5de
Kidneys 9.38b 330b 30.6a 0.53b 4.44bc 3.67a 310b 234a
Spleen 7.57b 406a 30.8a 0.29b 22.8a 3.60ab 409a 112c
Tongues 17.7b 184d 24.0a 0.31b 1.50bc 2.83ab 276b 102cd
P-value <0.001 <0.001 0.132 <0.001 <0.001 <0.001 <0.001 <0.001

Note: Means with different superscripts in a column differ significantly

Table 3: Mineral content of 100g edible portion cooked mutton offal

Ca P Mg Cu Fe Zn K Na
n=3 mg/100g mg/100g mg/100g mg/100g mg/100g mg/100g mg/100g mg/100g
Intestines 16.6b 112c 16.9cd 0.15b 1.69e 2.55b 50.2d 29.5e
Lungs 11.0bc 250b 19.4bcd 0.41b 10.7a 2.62b 285bc 190b
Hearts 6.00c 223b 24.8ab 0.65b 4.54c 2.74b 275bc 97.5cd
Livers 5.60c 399a 26.2ab 31.87a 7.96b 4.38a 326bc 78.7cde
Stomachs 24.6a 112c 15.9d 0.25b 2.70de 3.37ab 104d 58.7de
Kidneys 15.6b 400a 30.7a 0.56b 4.34cd 4.49a 279bc 270a
Spleen 6.00c 414a 31.4a 0.15b 11.7a 3.61ab 472a 112cd
Tongues 8.70c 142c 23.3bc 0.20b 1.81e 2.91b 235c 122c
P-value <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001

Note: Means with different superscripts in a column differ significantly

Table 4: Contribution to NRV’s and nutrient content claims per 90g cooked offal meat
INRV according to the Foodstuffs, Cosmetics and Disinfectants act (DOH, 2014)

Protein Calcium Phosphorus Magnesium Iron Manganese Zinc Potassium Sodium
NRVI 56g 1300mg 1250mg 365mg 13mg 2.3mg 10mg 4700mg 2000mg
Mutton % of NRV per 90g servingII III
Intestines 25IV 11 8 0 12 0 23 IV 1 1
Lungs 37v 7 18 IV 0 74 VI 0 24 IV 5 9
Hearts 33 0 16 IV 0 31v 0 25 IV 5 4
Livers 37v 0 29 IV 0 55v 0 39v 6 4
Stomachs 29 IV 2 8 0 19 IV 0 30v 2 3
Kidneys 52v 1 29 IV 0 30v 0 40v 5 12
Spleen 45v 0 30v 0 81 VI 0 32v 9 5
Tongues 25IV 1 10 0 13 0 26 IV 4 5
Lamb % of NRV per 90g servingII III
Intestines 23IV 1 9 0 10 0 23 IV 1 2
Lungs 34v 1 19 IV 0 58v 0 23 IV 6 7
Hearts 31v 0 14 0 27 IV 2 22 IV 5 5
Livers 38v 0 30v 0 42v 10 38v 6 3
Stomachs 40v 4 12 0 34v 8 35v 3 4
Kidneys 39v 1 24 IV 0 31v 2 33v 6 11
Spleen 47v 1 29 IV 0 158VI 0 32v 8 5
Tongues 31v 1 13 0 10 0 25 IV 5 5

 II 90g is the prescribed portion size for lean meat according to the Food-based dietary guidelines for South Africans (Schönfeldt, Pretorius, & Hall, 2013)

III Values do not take bioavailability into account

IV ” Source of” as per the Foodstuffs, Cosmetics and Disinfectants act (DOH,2014)

v “” High in” as per the Foodstuffs, Cosmetics and Disinfectants act (DOH,2014)

VI ” Excellent source” as per the Foodstuffs, Cosmetics and Disinfectants act (DOH,2014)

South African lamb and mutton offal can be considered a good source of protein and a nutrient dense food. In the case of protein, zinc and iron, three nutrients of concern in South Africa, all lamb and mutton organ meats were at least a source of two out of these three nutrients with lamb and mutton spleens and lamb and mutton lungs being excellent sources of protein. In view of the current disturbing state of nutrition in South Africa, as well as efforts to reduce food waste, lamb and mutton organ meats were found to be important food commodities and it was suggested that the promotion of offal should be prioritised.

Quantitative food data goes hand in hand with the nutrient composition tables used in a given country, because it provides supporting information on the food items included in the nutrient composition tables. Good quality nutrient composition and quantitative food data play an integral role in reporting the nutrient intake of a population, as well as interpreting results of certain epidemiological research. A new set of quantitative data on the nutrient and physical composition (meat, bone and fat fractions) and yield of different offal cuts were generated to assist researchers in collecting more precise, product specific data to measure nutrient in South African food consumption studies.

Please contact the Primary Researcher if you need a copy of the comprehensive report of this project – Beulah Pretorius on

Heartwater survey on changes and causes

A Survey of veterinary and farmer experiences and opinions on heartwater incidence, distribution and associated factors in domestic ruminants in South Africa

Industry Sector: Cattle and Small Stock

Research Focus Area: Animal Health and Welfare

Research Institute: Faculty of Veterinary Science, University of Pretoria Department of Production Animal Studies

Researcher: Prof     Gareth Bath     ECSRHM

Title Initials Surname Qualification
Dr D Coetzee BVSc
Dr T Brink BVSc
Dr R Leask M. Med. Vet
Prof G Fosgate PhD

Year of completion : 2017

Aims Of The Project

  • To establish the extent and incidence of HW by a structured questionnaire sent to farmers and veterinarians in heartwater areas

  • To establish changes that may have occurred in these areas

  • To identify possible reasons for the changes observed.

  • To make recommendations for further action

Executive Summary

The Questionnaire Survey achieved the aims set out for the project. Sample sizes, structure, demographics, geographic distribution and experience profiles of both Veterinary and Farmer groups were adequate for gathering useful data and for conclusions to be drawn.

There appears to be epidemiologically significant change in the spatial distribution of heartwater in many areas, with serious expansion in some, of up to 150 kilometres, and 48% of veterinarians and 42% of farmers reported seeing increases in the number of farms affected by heartwater. The disease is also increasing in incidence and severity judging by the number of cases seen, increases in occurrence observed and also some indication that there is an increased risk of heartwater in more months of the year than in the past.

Climate change as a causative factor, indicated by observations of increased average temperatures, milder frosts, less rain and shorter rainy seasons, was identified by the majority of farmers but not by as many veterinarians. Respondents in both groups considered vegetation change an important factor. Increasing wildlife, especially antelope, was seen as a major factor by most veterinarians and also many farmers. Both groups identified the movement of livestock and wildlife as an increasingly important factor that must be seen as of major concern for both industries since it leads to the avoidable spread of many diseases apart from heartwater. Movement controls must be reinstated and reinforced by vigorously enforced legislation.

The use of the heartwater ‘vaccine’ is either unchanged or in decline and is apparently causing an increasing reliance on dipping and block treatments. Farmers reported mainly an increase in tick control by dipping and rated this as a very important factor in the management of heartwater; the veterinarians rated it lower. Control achieved by routine, regular block treatments of entire flocks or herds was also seen as a major factor and as increasing in use for both respondent groups, each giving it a high ranking. Relying on intensive tick control and ongoing block treatments leads to loss of efficacy in key acaricides and antibiotics and has very serious implications and consequences for the control of many diseases and parasites of livestock. The lack of a commercially available, safe, effective, practical and affordable true vaccine for the protection of ruminant livestock against heartwater should be of the absolute highest concern and priority. After decades of trials, OVI researchers have developed a very promising candidate vaccine, yet its further development to the commercial stage appears not to be receiving the urgency and attention needed.

Diagnosis of heartwater in post mortem cases is accurate and reliable if backed by appropriate histopathological staining and examination, but far too few farmers have their suspicions confirmed by laboratory tests. This leads to a danger of widespread misdiagnosis and the disease being potentially either under- or over-diagnosed. The problem extends to clinical cases especially, where diagnosis rests mainly on a few ‘typical’ signs. The presence of atypical forms of heartwater further complicates the problem.

Popular Article

Is Heartwater spreading and becoming worse, and why?

A survey of farmers and veterinarians in heartwater-prone areas of South Africa indicates that the disease is expanding in geographic area and increasing in severity. What are the possible reasons for this, what has changed in these areas, and what should be done to limit the impact of a worsening situation? The Heartwater Survey was undertaken by staff of the Faculty of Veterinary Science at Onderstepoort, and generously funded by the financial subvention of RMRD – SA.

A representative sample of veterinarians and farmers with adequate experience in areas where heartwater is a problem agreed to take part in the survey. The survey took the form of a structured, measureable and analysable set of questions in a standard questionnaire. The questionnaire was designed to allow comparisons to be made between the two groups, who were for the most part asked the same or similar questions. The responses of these two groups gave an insight into the current heartwater situation as it is experienced by the farmers and veterinarians in the heartwater areas, and shed some light on the importance of factors believed to be involved in the expansion of areas affected by heartwater and in the changes of its severity.

It was deduced from the responses of both groups that the disease is expanding its range in many areas, and alarmingly so – by an average of perhaps 60km and as much as 150 kilometres in some regions. The reports by both vets and farmers indicated that an increasing number of farms are becoming affected by heartwater, confirming that the disease appears to be spreading. It was also evident that annual losses caused by heartwater can be very high on some farms unless the disease is suppressed by unsustainable practices like intensive dipping or repeated blocking of entire herds and flocks with tetracycline antibiotics. Both groups also reported that the number of cases of heartwater is rising.

Several factors that were thought to be responsible for these changes were identified by the two groups, although they did not always agree on the relative importance of these factors. Climate change, evidenced by higher than average temperatures, milder frosts, lower rainfall and shorter rainy seasons, was seen as a major causative factor by most farmers but considered to be of less significance by the veterinarians. Both groups saw a change in vegetation as an important factor but more so by the vets, who also rated the role of increased wildlife and the movement of antelope as a major factor, more so than the opinion of the farmers. The groups were, however, in agreement about the important role played by the movement of livestock in the potential to increase the areas affected by heartwater.

The survey revealed that the use of the heartwater “vaccine” was stagnant or in decline, which is not surprising in view of the many difficulties encountered in its use, the risks and dangers inherent to it, and the uncertainties around its efficacy. Unfortunately this reluctance to use the vaccine has evidently led to an increasing use of frequent, suppressive tick control or reliance on regular blocking treatments for heartwater for entire herds or flocks. Neither of these control measures are sustainable in the long run, and are almost certain to hasten the onset and rapid development of drug resistance in the bont tick and the heartwater organism. It was also clear from the survey that the diagnosis and treatment of heartwater relies far too heavily on the clinical signs or symptoms seen, especially with the farmers, leading to the dangers of misdiagnosis.

In conclusion, the survey revealed that heartwater is increasing in both its geographic extent and its severity, at least in some areas, and that a number of factors appear to be involved in causing these changes. Chief of these were climate, vegetation, and wildlife and livestock movements. The role of static or declining vaccine usage, leading to an increased reliance on intensive tick control, or alternately the widespread use of whole herd blocking with tetracycline antibiotics was also revealed by the responses of both groups.

The most pressing need now to bring about satisfactory heartwater control is the rapid and prioritised development of a commercial vaccine by OBP that is safe, effective, practical, easy to use and affordable. This development can be based on the very promising candidate vaccine developed by OVI. Ensuring that the movement of both wildlife and livestock is properly controlled to try to reduce the spread of the disease is another priority requiring urgent attention.

Please contact the Primary Researcher if you need a copy of the comprehensive report of this project – Gareth Bath on

Amino acid composition of South African beef

Determining the amino acid profile of selected cuts from four age groups of South African beef, as additional to the previously approved project on the nutrient content of South African beef, in order to determine protein quality.

Industry Sector: Cattle and Small Stock

Research focus area: Red Meat Safety, Nutritional Value, Consumerism and Consumer Behaviour

Research Institute: Animal and Wildlife Science, University of Pretoria

Researcher: Prof Hettie Schönfeldt PhD

Team members

Title Initials Surname Qualification
Dr N. Hall Ph.D
Dr B. Pretorius Ph.D

Year of completion : 2017

Aims Of The Project

  • To determine the amino acid profile of South African beef
  • To determine the validity of using nitrogen and a specific Jones factor to define protein quantity
  • To determine the protein quality of South African beef in the context of human nutrition

Executive Summary

Globally protein quality is under the spotlight. The importance of protein quality was emphasized by both the 2007 and the 2011 Food and Agriculture Organization/ World Health Organization (FAO/WHO) Protein and amino acid requirements in human nutrition reports. These reports questioned the validity of current measures to determine crude protein content and protein absorption, and called for more research. Locally, the national Department of Health Directorate Food Control’s most recent legislation on food labelling and advertising requires that in order to make protein content claims, amino acid data in addition to crude protein (nitrogen), is needed.

During this project, raw and cooked beef cuts (prime rib, rump and shoulder) from all four age groups according to the South African classification system were sent for amino acid analyses at the ARC Irene Analytical laboratory.

Aligning with international debates, a literature review was completed to investigate existing literature on the validity of using the Jones factor of 6.25 to quantify the amount of protein from nitrogen within the red meat matrix. Amino acid data obtained was also compared to the use of the Jones factor to quantify the total protein content of red meat, and alternative factors were explored – similar to what has been done by Sosulki et al. in 1990. Mariotti et al (2008) also queried the use of 6.25 as the converting factor for red meat. Our study found that complete amino acid profiles of local beef amounted to 91% on average of protein based on total Nitrogen content (in weight). This indicates that there is an overestimation of protein in beef when the conversion factor of 6.25is used.

For local legislative purposes, the study found that all cuts from all age groups contain adequate quantities of the essential amino acids as required by the R.429 Food Labelling Legislation. This provides the scientific evidence required for South African beef to make protein content and functional protein claims on packaging and in marketing activities.

Technology transfers

  1. Participation of the Human Nutrition and Health Committee Meeting of the International Meat Secretariat (Canada, 1-3 July, 2015) (Addendum 2)
  2. Participation of the Human Nutrition and Health Committee Meeting of the International Meat Secretariat (Oslo, Norway, 15-18 July, 2016) (Addendum 2)

Reports to Industry

  1. NRF-THRIP progress report 2014
  2. NRF-THRIP final report 2015
  3. RMRD SA Progress report 2014
  4. RMRD SA Progress report 2015

Scientific articles

  1. Schönfeldt H.C., Pretorius B. and Hall, N. (2016) ‘Bioavailability of Nutrients’, In: Caballero, B., Finglas, P., and Toldrá, F. (eds.) The Encyclopedia of Food and Health vol. 1, pp. 401-406. Oxford: Academic Press.
  2. Article to be submitted after presenting “Updating and expanding the Food Composition Table for Western Africa“ at International Food Data Conferences (IFDC) – Official INFOODS conference. Center for Science in the Science and Technology Pole, Buenos Aires, Argentina. 11-13 October 2017.
  3. Article to be submitted after presenting “Amino acid and protein content of lean beef“ at International Food Data Conferences (IFDC) – Official INFOODS conference. Center for Science in the Science and Technology Pole, Buenos Aires, Argentina. 11-13 October 2017.


  1. Hall, N. 2015. Sustainable red meat from a nutrition perspective. University of Pretoria.

Conferences, symposia

  1. Co-author FAO/INFOODS (2017) Updating and expanding the Food Composition Table for Western Africa. 12th International Food Data Conference (IFDC) – Official INFOODS conference.
    Center for Science in the Science and Technology Pole, Buenos Aires, Argentina. 11-13 October 2017.
  2. Schönfeldt, H.C., Hall, N., Pretorius, B. and Van Deventer, M.M. (2017) Amino acid and protein content of lean beef. 12th International Food Data Conference (IFDC) – Official INFOODS conference. Center for Science in the Science and Technology Pole, Buenos Aires, Argentina. 11-13 October 2017.

Literature review

  1. Hall, N.G. and Schönfeldt, H.C. (2013) ‘Total nitrogen vs amino-acid profile as indicator of protein content of beef’, Food Chemistry. 140 (3): 608-612.

Popular Article

Globally protein quality is under the spotlight

Hettie Schönfeldt, Beulah Pretorius, Nicolette Hall, Maricia van Deventer

Department of Animal and Wildlife Sciences, Institute of Food, Nutrition and Well-being, University of Pretoria.

There has been much discussion regarding protein and amino acid requirements for both adults and children over the past few years.

Conventionally, protein content is determined by analysing the total nitrogen content in a food, and multiplying this by a standard conversion factor to obtain protein quantity – referred to as “crude protein”. Because proteins are made up of chains of amino acids, they can be hydrolysed and the separate amino acids can then be measured. The sum of the amino acids then represents the protein content (by weight) of the food. This is sometimes referred to as a “true protein”. This method however needs sophisticated equipment and is more expensive.

A project at the University of Pretoria aimed to determine the protein content and amino acid profile of South African beef (raw and cooked) and to establish if different cuts in the carcass and/or age of the animal influences the amino acid profile of South African beef.

Crude protein and amino acid analyses were done on 36 meat samples from Bonsmara carcasses from fat code two and all four age groups according to the South African Carcass Classification System. Three cuts (rump, prime rib and shoulder) were selected from each carcass and analyses were done on both raw and cooked meat.

Age had no significant effect on the sum of all amino acids (true protein) in both raw and cooked cuts. In the cooked cuts crude protein were found to be significantly different between the age groups for the different cuts. It should however be noted that these differences, although statistically significant, probably have little relevance in terms of human dietary requirements for protein as they differ by less than 2 g per 100 g cooked meat.

The data generated by this study is of further interest as discussions regarding the validity of nitrogen analyses for protein quantity determination and methods used to assess protein quality unfold. Table 1 shows the percentage of total amino acids to protein calculated with the Jones factor. It would be more appropriate to base estimates of protein on amino acid data.

Table 1: Percentage of sum of amino acids (‘true protein’) to protein calculated from total nitrogen using the Jones-factor (‘crude protein’)

Cut Raw / Cooked Percentage (Sum of amino acids / protein calculated from total nitrogen x 100)
Rump Raw 95%
Cooked 89%
Prime rib Raw 97%
Cooked 90%
Shoulder Raw 94%
Cooked 89%

Instead of simply focussing on total protein, attention has shifted to the greater importance of protein quality than actual quantity, emphasising the presence of individual amino acids in a food. One method of measuring protein quality is determining the quantity of the total essential amino acids and the digestibility of the protein source (PDCAAS). Data on the amino acid composition of foods is therefore essential in order to contribute to the current global discussion.

Protein quality answers two important questions namely, how much protein as well as what kind of protein should be consumed. Dietary proteins are classified as either being complete or incomplete. Some foods, such as animal source food, contain all indispensable (essential) amino acids and are referred to as a complete protein. Plant foods, on the other hand, lack one or more essential amino acid, which renders these sources of protein “incomplete”. Amino acids containing sulfur (including methionine and cysteine) and lysine most commonly limit the nutritional value (quality) of proteins in the human diet. Concentrations of these amino acids are, generally, considered lower in plant foods than in food of animal origin. In table 2 the lysine, methionine and cysteine content of commonly consumed food products is reported. Other essential amino acids, lysine and tryptophan, are also consistently found at lower concentrations in plant-based rather than animal-based foods. For example, tryptophan and lysine are limiting in corn; lysine in wheat, sorghum, and other cereals; and methionine in soybeans and other legumes. Including a small amount of lean beef in combination with plant-based foods can increase the protein quality of the meal.

Table 2: Lysine, methionine and cysteine content of commonly consumed food products

Food source  Food Range (mg/100g) from different studies
Lysine Methionine Cysteine
Animal products Beef and Veal (edible flesh) 531–591 147–182 78–182
Chicken (edible flesh) 384–606 88–215 64–114
Offal 375–506 138–181 62–132
Mutton and lamb (edible flesh) 438–589 131–198 63–144
Hen eggs 375–467 181–249 113–189
Fish (fresh, all types) 380–689 120–290 28–144
Legumes Chick-pea 406–463 34–106 50–94
Cowpea 394–479 50–119 48–106
Soya bean 313–477 53–114 51–114
Cereals & grain products Barley 159–250 63–250 81–194
Maize 100–214 53–175 38–200
Millet 100–244 84–246 69–169
Rice (brown or husked) 198–263 117–194 30–79
Rye (whole meal) 151–281 59–181 85–156
Wheat (whole grain) 131–249 63–156 111–212
Roots and tubers Potato 163–488 54–125 7–81

The protein and indispensable amino acid profile of lean beef is reported in table 3. This is compared to the recommended protein requirement of 0.66 g/kg body weight/ day and the amino acid scoring pattern for children older than 3 years, adolescents and adults. According to the South African Food Based Dietary Guideline a serving of red meat can be eaten daily, but should not be more than 90g/day.

Table 3: Dietary protein and indispensable amino acid profile of cooked beef, cow’s milk, cooked soya beans compared to the recommended amino acid scoring pattern for children (3-10years), adolescents and adults

Cooked lean beef Full cream cow’s milk Cooked soya beans Recommended protein and amino acid scoring pattern for older children, adolescents and adults
“Crude” protein (g/100g) 31.8 3.25 18.21 0.66 g/kg/day50kg person = 33g

70 kg person = 46g

Amino acid
(mg/g total protein)
Histidine (His) 28 28 25 16
Isoleucine (Ile) 44 54 44 30
Leucine (Leu) 74 94 74 61
Lysine (Lys) 97 79 61 48
Sulphur amino acids (SAA) Methionine (Met) + Cysteine (Cys) 63 39 27 23
Aromatic amino acids (AAA) Phenylalanine (Phe) + Tyrosine (Tyr) 73 97 83 41
Threonine (Thr) 44 48 40 25
Tryptophan (Thp) 16 12 13 6.6
Valine (Val) 46 59 46 40

The study found that South African beef from all age groups adheres to the requirements as set out by the Department of Health to be labelled and proclaimed as a complete, quality protein.

It is of interest to note that the true protein was consistently lower in the cooked meat compared to the raw meat and that the different cuts varied in the respective amino acid profiles. While the measurement of crude protein (total nitrogen multiplied by a factor) is adequate for many purposes, amino acid data would provide a better assessment of the nutritional value of a food. Through this study the amino acid profile of South African lean beef was determined and is available for future studies.

Acknowledgement: This study was funded by Red Meat Research and Development of South Africa (RMRD SA) and the National Research Foundation Technology and Human Resources for Industry Programme (NRF-THRIP) (Project id: Tp1208076284).

Please contact the Primary Researcher if you need a copy of the comprehensive report of this project – Prof H.C. Schonfeldt on

Genomics for the South African Beef industry

Establishing genomic selection for the South African beef industry

Industry Sector: Cattle and Small Stock

Focus Area: Livestock production with global competitiveness (2)

Research Institute: Department of Animal & Wildlife Sciences, University of Pretoria (UP) and SA Studbook Association

Researcher: Prof Este van Marle-Köster PhD

Research team:

Title Initials Surname Highest Qualification
Dr Japie van der Westhuizen PhD

Final report approved: 2016

Aims of the Project

  • To use high throughput SNP technology to establish reference populations for the SA beef industry.

Executive Summary

The project titled “Establishing genomic selection for the South African beef industry” was conducted at the University of Pretoria, Department of Animal & Wildlife Sciences in collaboration with South African Stud Book and Animal Improvement Association.

The overall aim was to use high throughput SNP technology to establish reference populations for the SA beef industry. To attain this goal, a process for the identification of high impact animals was established, guidelines for sample collection were compiled and genotyping were performed with the available funding using both 80K SNP and 150K SNP GeneSeek (GeneSeek GGP HD) bead chips at GeneSeek (USA. Population structure analyses were performed and parameters for genetic diversity and inbreeding were calculated.

Results has shown that breeds such as the Bonsmara and SA Hereford formed separate clusters while the other indigenous breeds such as the Tuli, Afrikaner and Drakensberger showed a closer relationship. These results are important for future across-breed analyses. The commercial chips also tended to be less informative for the indigenous breeds with regard to the number of SNPs available for analyses, but still had sufficient numbers for application in genomic selection. A substantial number of genotypes have been generated for Bonsmara cattle that have also been phenotypically recorded for the traits of interest.

In this project, the Bonsmara genotypes are currently being applied as a training set for estimation of Genomic Breeding Values (GEBV’s). After GEBVs have been estimated for these animals, validation will commence followed by the roll-out of routine GEBV estimation. This genomic information will provide breeders with an additional, accurate tool for selection of superior stock.

Popular Article

Genomic selection: a new tool for genetic improvement of SA Livestock

Este van Marle-Köster (PhD Pr.Anim. Sci.) & Carina Visser (PhD Pr.Anim. Sci)

Department of Animal & Wildlife Sciences, University of Pretoria


Over the past two decades major discoveries and technological developments in the field of molecular genetics opened up new opportunities for genetic improvement in farm animals that were previously beyond the reach of animal breeders. The bovine genome has been mapped and sequenced and several DNA-marker types were discovered. The discovery of Single Nucleotide Polymorphism (SNP) markers and the concurrent development of appropriate high through-put technology gave rise to commercial SNP chips available for generating genomic information.

SNP markers and genomic selection

The DNA markers used for generating genomic information for genomic selection are single nucleotide polymorphisms (SNP) commonly referred to as “SNIPS”. Each of these markers has two alleles and they occur very frequently across the genome. The Bos Taurus genome has an estimated total of nearly 4 million SNPs. It is currently estimated that a trait of economic importance (i.e. weaning weight, carcass weight, feed conversion ratio etc.) is governed by between 100 and 300 genes. Each of these genes contributes only a small amount to the phenotype that is expressed. In the past, individual genes and markers associated with genes were identified and thus only a very small portion of the phenotypic variation could be explained. By using a very dense SNP panel to genotype animals with, it is assumed that each individual SNP will be associated with at least one gene contributing to the trait of interest. When all the SNP effects are added, they should thus explain the total phenotypic variance that is expressed.

If a number of animals of a specific breed have been genotyped, and their phenotypic records are available, it is possible to draw a correlation between a SNP combination and the level of performance associated with it. This correlation is commonly referred to as the “prediction equation” or “SNP key”. Genomic selection is therefore based upon the basic principle of using the information of many DNA markers and accurate and complete phenotypic records. In practical breeding, the genotypic information (Direct Genomic Value) will be included in the Estimated Breeding Value (EBV) of an animal. In this way, genomic data will be included as an additional source of information together with pedigree and performance records used in routine quantitative analyses. This process is referred to as blending and will result in providing a genomic estimated breeding value (GEBV) for each individual.

Prerequisites for implementation

The implementation of genomic selection is not a simple process and each phase requires careful planning to ensure that the end result will be accurate, useful and cost effective. The first step is the selection of the bulls to form the reference or training population. These bulls should represent the specific breed and include bulls with low, medium and high breeding values with accuracies above 60%. It is important that the traits recorded on these bulls will be the traits that breeders would like to include in selection programs and which form part of the breeding objectives for the breed. A biological sample of these animals should be available and this could be a hair, blood, semen or tissue sample for extraction of DNA.

Once the DNA is available the samples will be analyzed using an appropriate high density commercial chip. In this step the SNP effects based on high density chips and their correlation with the animals’ known performance (EBV values) are established, in order to calculate the prediction equation.

Application of SNP technology

There is no doubt that genomic selection has significant advantages for improvement of farm animal genetics. Dairy cattle thus far have led the way and have experienced some of the advantages of having an added source of information. GEBVs can be obtained in a relative short period after birth compared to a 6-7 year period of progeny testing before a progeny-based EBV becomes available. GEBVs have distinct advantages for dairy cattle with regard to reducing costs on progeny testing and decreasing the generation interval. Genomic technology has been well received by dairy cattle breeders in the USA and Canada and indications are that genomic evaluations will replace traditional evaluations in these countries. The use of genomic selection in selection programs holds the most potential for sex-limited traits, traits that are expressed late in life and traits with low heritability.

In South Africa we are fortunate to have a long history of animal recording for a large number of cattle breeds. This data has routinely been used for EBV calculations and are widely used by South African stud breeders. The current challenge is to ensure the banking of biological samples of animals with desired traits and phenotypes, in order to obtain both molecular and phenotypic records from individuals. Application of GS globally in both the dairy and beef industries has become inevitable and smaller countries with fewer resources, like South Africa, will have to collaborate and carefully plan genetic programs to remain part of the international arena.

If you have any queries, please contact the researcher Prof Este van Marle-Köster PhD on