Search

Breeding of beef cattle is changing, with more emphasis on efficiency of production. Feed cost is the highest expense, and reducing it has the potential to increase profitability. Common measures of efficiency are ratio traits such as feed conversion (feed consumed/weight gain) and feed efficiency (weight gain / feed consumed). Feed conversion ratio is commonly used in South Africa in an attempt to improve feed efficiency. These ratio traits are associated with growth rate. Selection for them would result in higher growth as a correlated response and might also increase the mature size of the cows and their maintenance cost. Thus, alternative efficiency traits such as residual feed intake and residual daily gain have been proposed. In this study, variance components, and genetic parameters for feedlot traits for the South African Simmentaler breed were estimated, with emphasis on the efficiency traits. The focus was to evaluate the use of residual feed intake as an alternative trait. The results indicate non-significant correlations between residual feed intake and body weight and growth traits, implying that residual feed intake should have little effect on the other traits. This is in contrast to the moderate to strong correlations of feed conversion ratio with the same traits. The study demonstrates that considerable genetic variation exists for residual feed intake, which can be exploited. Selection for residual feed intake can reduce the carbon footprint of beef due to the associated lower methane emissions.

Individual and maternal breed additive effects and heterosis exist for most economically important traits in cattle. Crossbreeding may therefore be valuable for emerging and commercial beef farmers in improving the productivity of their herds. Calves were produced by mating Afrikaner, Bonsmara and Nguni cows to Afrikaner, Bonsmara, Nguni, Angus and Simmental bulls. The cows used were from Vaalharts Research Station or were purchased from other herds. Data were collected over three years. Individual and maternal additive effects and individual heterosis were estimated simultaneously as continuous linear variates. The estimated genetic effects were then used to predict production levels that may be achieved through implementation of top-cross, two-breed rotation, and terminal sire crossbreeding systems. The individual estimates of the genetic effects were relatively small and in most cases were not different from zero, with the exception of the maternal additive effects of Nguni on preweaning traits and their individual additive effect on cow weight, which were less than those of Bonsmara. However, the alternative crossbreeding systems differed across traits. The straight-bred breeding system was least efficient, followed by the crisscross system (+2%) and the terminal sire system that utilized Simmental (+4%), with the terminal sire system utilizing Angus being on average most efficient (+8%). The inter-generational genetic differences in cow weight that resulted from the use of different breeds of sire increased its standard deviation by 5 to 6% in rotational crossing. Despite the relatively small magnitude of the genetic effects, advantages of crossbreeding systems became evident.Keywords: breed additive, crossbreeding, heterosis, post-weaning, pre-weaning

Wet carcass syndrome (WCS), which is observed predominantly in sheep, affects carcass quality negatively. After slaughter the carcass appears to be ‘wet’ with a subcutaneous accumulation of watery fluid. Not all animals in a contemporary group are afflicted, and experimental attempts to induce WCS have been unsuccessful. The reported prevalence of WCS in Dorper and Dorper crosses gave rise to the hypothesis that it may have a genetic basis. Therefore, the primary objective of this investigation was to test this hypothesis using a high-density SNP assay to search loci that may predispose sheep to WCS. Muscle samples from 43 afflicted and 41 unafflicted sheep were collected from slaughterhouses in the province of Northern Cape, South Africa, and in southern Namibia. Tests against candidate genes proved uninformative, as did runs of homozygosity. Potential associations between WCS and an autosomal genetic marker were investigated further in a case-control genome-wide association study. Separate analyses for each sex were motivated because single nucleotide polymorphisms (SNPs) on the X chromosome suggested quantitative trait loci. These analyses revealed significant associations between SNP and WCS in males, but not in females. Three SNPs that reached genome-wide significance in males are in strong linkage disequilibrium with the Duchenne muscular dystrophy, 5-hydroxytryptamine receptor 2C, and Teneurin transmembrane protein 1 genes. These genes are identified as positional candidate genes, and the Duchenne muscular dystrophy, 5-hydroxytryptamine receptor 2C genes have biological effects that have been documented in other species, making them plausible functional candidate genes for WCS in sheep.Keywords: association analysis, Dorper, sheep carcass, single nucleotide polymorphisms, X chromosome

The purpose of the study was to investigate the effects of three levels of lick supplementation on the production and reproduction of cows grazing transitional Cymbopogon-Themeda veld. The study was conducted over three years (2011–2014). A total of 150 Drakensberger cows were randomly allocated to three supplementary treatment groups. These supplementation formulations are available commercially and are typical of levels used under farming conditions. In summer Treatment 1 (T1) consisted of a supplement containing 50 g phosphate (P)/kg and 150 g crude protein (CP)/kg. T2 and T3 both consisted of supplements containing 60 g P/kg and 0 g CP/kg. In winter, T1 consisted of a supplement containing 367 g CP/kg, 77.5% non-protein nitrogen (NPN) and metabolizable energy (ME) content of 5.25 MJ/kg. T2 had 466 g CP/kg, 88.7% NPN and a ME content of 4.4 MJ/kg. T3 had 475 g CP/kg, 95.9% NPN and an ME content of 2.4 MJ/kg. Traits were calf birth weight, 100-day and weaning weights of calves, cow weight at weaning, inter-calving period (ICP), conception rate and body condition score (BCS) of cows. Calf birth weight was affected by supplementation treatment only in year 3 and 100-day weight in year 2. However, weaning weight and reproductive performance were not influenced by treatment. It was concluded that the level of supplementation of each treatment group enabled the cows to operate within their target weight range; however, it was more profitable to use the T3 supplementation option. Keywords: Cymbopogon-Themeda veld, cows, performance

The Afrikaner is one of three indigenous cattle breeds found in South Africa. Afrikaner cattle were originally extensively used for crossbreeding purposes and breed development. The objective of this study was to determine the genetic diversity of selected stud and commercial herds from the whole South African Afrikaner population, as well as to determine the genetic structure among these herds. Assignment methods (based on STRUCTURE software) revealed a real structure consisting of four genetic populations (K = 4). Estimates of genetic diversity did not support the hypothesis of significant loss of genetic diversity in any individual Afrikaner herd. Heterozygosity estimates ranged from 0.456 - 0.737 within individual populations, with an overall heterozygosity estimate of 0.568 for the Afrikaner breed. The average number of alleles per locus was regarded as being 2.67 - 7.78, with an average of 5.18 alleles per locus. It could be concluded that a moderate to high degree of variation is still present within the Afrikaner cattle breed, despite the recent decline in numbers of this indigenous breed.Keywords: Bos taurus africanus, heterozygosity, inbreeding, microsatellite markers

The purpose of the study was to investigate a possible genotype by environment interaction in first calf South African Holstein cows for both production and reproduction traits. Data from 100 975 cows on a total mixed ration (TMR) and 22 083 pasture based cows were used. These cows were the progeny of 4 391 sires and 84 935 dams produced over a period of 11 generations. Traits analysed were milk production (corrected to a 305-day equivalent) and age at first calving (AFC). Both were recorded over a period of 30 years from 1980 - 2010. Production or AFC in each environment (TMR vs. pasture) was treated as a separate trait. Bivariate analyses, fitting an animal model using the ASREML software, were used to obtain genetic correlations between the traits measured in each environment. The fixed factors included were a concatenation of breeder-keeper-year for both milk production and AFC and age at first calving which was fitted as a linear regression for milk production. The random part consisted of the direct additive effects only. The genetic correlation for milk production measured in the two different environments was 0.90 (0.027) and that of age at first calving 0.28 (0.12). The heritability estimates for milk production were 0.23 (0.008) under the TMR system and 0.32 (0.015) for the pasture based system, while the estimates for AFC were 0.063 (0.005) and 0.055 (0.009), respectively. The rather large-scale effect in the heritability (0.23 → 0.32), as well as the correlation of less than one for milk production between the two environments, indicates that a G x E may exist. However, the low genetic correlation between the two environments for AFC is much more real and indicates that G x E should be taken into account when sire selection is performed.Keywords: Age at first calving, milk production, total mixed ration, pasture

The purpose of this study was to evaluate alternative expressions of genetic merit for cow efficiency. Weights of Pinzgauer cattle taken at birth, weaning, and maturity were extracted from the South African National Database. Average daily gain from birth to weaning (ADG) and cow weight (CWT) were analyzed with a multi-trait mixed model. The model included direct and maternal genetic effects, a permanent environmental effect attributable to dams on ADG, a direct genetic effect and a permanent environmental effect attributable to there being multiple observations from the same cow on CWT as random effects. Heritability estimates for direct and maternal additive effects on ADG were 0.27 ± 0.04 and 0.06 ± 0.02, respectively. The estimated heritability for CWT was 0.45 ± 0.06. Estimates of repeatability for ADG and CWT were 0.42 and 0.67, respectively. Estimated breeding values based on the preceding results and using the maternal genetic effect on ADG as a proxy for the direct genetic effect on milk production were combined in six indexes of cow efficiency. These indexes sought to increase output and decrease input simultaneously, to increase output holding input constantly, and to hold input constant while decreasing input. The diversity of emphasis applied across these indexes suggests the need for due diligence in developing breeding objectives for improvement of cow efficiency. Indexes that are consistent with the econometric definition of efficiency and seek to simultaneously increase output and reduce input are recommended. ______________________________________________________________________________________ Keywords : genetic parameters, multiple trait selection, Pinzgauer, selection index

The wildlife industry in South Africa has shown immense growth since the 1990s, which was brought about by the private game segment of the industry. In recent years, trophy quality Cape buffalo breeding animals have achieved extremely high prices. Much of the economic value of these animals can be attributed to horn size, which is important for breeding and hunting purposes. The main objective of the study was to estimate variance components for horn traits of economic importance as well as to develop guidelines for recording these traits. To date, no quantitative genetic analysis has been done for any traits in Cape buffalo. The total number of horn measurement records included in the evaluation was n = 945 for outer spread (BHSO), n = 470 for tip to tip (BHTSCI), n = 468 for left boss and n = 479 for right boss. For descriptive statistics, males and females were considered separately while age was divided into clusters of six months. A multi-trait animal model using Monte Carlo Markov Chains methods was used for the estimation of genetic parameters. Results suggest that it is not economically viable to measure horn spread and tip to tip of females after 48 months of age. Horns of the males continue to grow beyond 91 months of age. Boss records were unreliable owing to the applied measurement techniques for female and young animals. An inbreeding coefficient of 0.008 was calculated, suggesting adequate genetic diversity in the studied population. The heritability estimates of the horn traits were low, showing that extreme care has to be taken to develop effective selection programmes for the buffalo game industry using their horn genetic parameters. Further quantitative studies are required to support the results of the current study. Keywords: genetic correlation, genetic parameters, heritability, Monte Carlo Markov Chain

Much of the economic value of wildlife can be attributed to horn size, which is an important trait for trophy hunters. The main objective of the study was to estimate genetic parameters for the economically important horn traits of sable antelope that are currently being measured in the South African industry. To date, no quantitative genetic analysis has been done for any traits in sable antelope. The total number of records included in the evaluation were n = 1713 for horn length (SHL), n = 1503 for circumference (SHC), n = 1486 for tip to tip (SHTT), n = 1505 for tip length (SHT), and n = 1447 for rings (SHR). Males and females were considered separately in six-month age clusters. A Markov chain Monte Carlo (MCMC) multi-trait analysis was used to estimate (co)variance parameters for the horn traits. The results indicate a sex effect for all the traits and suggest that it is not economically viable to measure horn length of either sex after 54 months old. The horns of females are on average 40% shorter compared with bulls at maturity. Continuous horn growth throughout the lifetime of sable is suggested by the formation of ring posts, but is often masked by horn attrition and inadequate measuring techniques. An inbreeding coefficient of 0.0043 suggests adequate genetic diversity in the studied population. Heritability estimates of horn traits varied from 0.085 to 0.52, while genetic correlations ranged from 0.1 to 0.6 with the highest correlation being found between horn length and tip to tip. Further studies are recommended to confirm these results. Keywords: Game, genetic evaluation, heritability

Heat stress, as a consequence of global warming, can have a profound effect on dairy cattle in South Africa. In this paper, current milk production data of Holstein dairy herds on pasture in South Africa, together with climate variables related to heat stress, were used to model and identify geographical areas for optimal milk production under current and future climatic conditions. To model the influence of heat stress on milk production of Holstein dairy herds on pasture in South Africa, the maximum entropy (Maxent) modelling technique was used in a novel approach to model and map optimal milk-producing areas. Geographical locations of farms with top milk-producing Holstein herds on pasture were used as presence-only data points. Only three of a possible eight climate variables that made significant contributions to the model were included, namely evaporation rate, relative humidity and mean annual temperature. The modelling technique showed good capability to capture the geographical influence of heat stress on milk production of Holstein dairy cattle and to reconstruct this relationship in sites where no data were available. The method performed well with low test omission rates, an area under curve (AUC) value of 0.929, and mean training data predictive rate of 0.66 (SD = 0.13). The modelled map indicated optimal milk production areas in the eastern parts of South Africa, which correlates well with the geographical influence of heat stress as represented by the temperature humidity index for the country. Future climate change projections (2046–2065) were used to predict optimal milk-producing areas for the future, indicating progressive shrinking of currently suitable areas and a geographical shift towards the southern parts of the east coast of South Africa. Possible long-term viable alternatives are suggested, including changes in nutrition and replacing existing breeds with more heat tolerant genotypes. Keywords: climate change, climate variables, Maxent modelling, temperature-humidity index

The importance of containing costs through the optimal utilization of feed emphasizes the need to optimize, rather than maximize, the rate of reproduction. It is, however, unknown which lick supplementation regimen, provided to an extensive beef herd on mixed veld, could bring about the most profitable and efficient farming enterprise. The aim of the study was thus to determine what lick supplementation regime would be most profitable in an extensive beef production system maintained on transitional Cymbopogon-Themeda veld. The different lick supplementation regimens offered differed in crude protein (CP) content, percentage non-degradable protein (NDP), metabolisable energy (ME) content, and recommended daily intake. A herd of Drakensberger cows and heifers was divided into three treatment groups (Treatment A, Treatment B and Treatment C), with 70 animals (n = 70) per treatment group. The CP, NDP, ME content of the licks provided in Treatment A were higher than those provided in Treatment B and C, while the CP, NDP, ME content of the licks provided in Treatment B were higher than those provided to Treatment C, but lower than those provided to Treatment A. The first two years’ (2011 - 2012 and 2012 - 2013) preliminary results indicate no significant differences in parameters that affect cow herd performance (weaning weight, cow herd pregnancy rate, intercalving period) between treatments. However, substantial cost differences in the lick supplied between treatments was recorded; thus, affecting profitability. Significant differences between treatments in the pregnancy rates of the first-calf heifers was recorded in the second year, and indicated that providing protein in a drought during summer to first calf heifers may increase the calving rate and hence profitability.Keywords: Beef cattle, cow herd production, extensive farming, lick supplementation, profitability

Agriculture is responsible for 5% to 10% of the global anthropogenic greenhouse gas (GHG) emissions. Livestock contribute about 65% of agricultural GHG and enteric fermentation accounts for 90% of this. The global warming potential of CH4 is known to be 23 times more than that of carbon dioxide, resulting in it being a significant role player in the greenhouse gas family. The laser methane detector (LMD) is an instrument that has the potential to measure enteric CH4 emission from livestock under normal husbandry activities. This study was aimed at evaluating the efficiency and results, when using the LMD to measure CH4 production under normal production conditions. Twelve heifers, four each from the Bonsmara, Nguni and Jersey breeds, were subjected to grazing natural veld, forage sorghum under irrigation, oats pasture under irrigation or a total mixed ration. Measurements were taken late afternoon (18:00) when the animals were ruminating. Four repeated measurements, lasting 60 seconds each, were taken on 10 consecutive days on each of the production systems. The animals were adapted for a period of 14 days on the specific feed, before the measurements were taken. The Jersey heifers produced significantly less CH4 than the Bonsmara and Nguni on natural veld, with no significant differences between breeds on the forage sorghum. On natural veld the heifers generated 48% more CH4. These results thus indicate that the LMD produce sensible and repeatable measurements that can be interpreted in respect of CH4 production by cattle. The next step will be to increase the number of breeds, numbers per breed, and feeding strategies over all seasons in order to validate and build up a baseline data set on the use of the LMD to measure CH4 emissions from cattle under different grazing conditions.Keywords: Heifers, methane emission, pastures, total mixed ration

Primary beef cattle farming in South Africa is largely extensive, whereas dairy farming is based on both total mixed ration and pasture production systems. Under natural rangeland conditions, decomposition of manure is aerobic, which produces carbon dioxide (CO2), part of which is absorbed by the regrowth of vegetation rather than released into the atmosphere, and water (H2O) as end products. Thus the cow releases methane (CH4) and the manure CO2. This is in contrast to intensive cow-calf systems in large parts of Europe and North America, where large quantities of manure are stockpiled and undergo anaerobic decomposition and produce CH4. Thus both the cow and the manure release CH4, which result in a higher carbon footprint than the extensive cow-calf systems. In dairy farming, increasing cow efficiency through intensive feeding (same kg milk output by fewer animals) can reduce farm CH4 production by up to 15%. In addition, when differences in productivity are accounted for, pasture systems require more resources (land, feed, water, etc.) per unit of milk produced and the carbon footprint is greater than that of intensive systems. This raises the question as to why the carbon footprint of intensive dairy cow production systems is less, but the carbon footprint of intensive beef cow-calf production systems is higher. The explanation lies in the differences in production levels. In the case of beef cows the weight of the intensive cows will be ± 30% higher than that of the extensive cows, and the weaning weight of their calves will also differ by ± 30%. In the case of dairy cows the weight of the intensive cows will be ± 20% higher, but their milk production will be ± 60% higher. The higher increase in production (milk) of intensive dairy cows, compared to the increase in production (calf weight) of intensive beef cows, explains the antagonism in the carbon footprint between different beef and dairy production systems. Unfortunately, carbon sequestration estimates have been neglected and thus the quantitative effects of these differences are not known.Keywords: Cow-calf production, methane, pasture production, production levels, total mixed ration

The goal of this research was to document the influence of Line 1 Hereford cattle, developed by the United States Department of Agriculture at its research facility in Miles City, Montana, on Hereford cattle in South Africa. Analytical approaches made use of both recorded pedigree and microsatellite marker information. Cattle with recorded performance data in South Africa were mated with Line 1 Hereford sires in silico and inbreeding coefficients were calculated for the resulting progeny. The relationship between South African and Line 1 Hereford cattle populations was estimated as twice the maximum inbreeding coefficient for the progeny of each South African animal. The calculated pedigree relationship of Hereford cattle registered in South Africa with Line 1 was 24%. Thirty-six South African Hereford cattle and a sample of 64 Line 1 animals were genotyped with 34 microsatellite markers. Based on a Bayesian model-based clustering method, the probability that the South African Hereford cattle were members of Line 1 was 0.38 ± 0.08. This research documents one aspect of the far reaching effects of the Line 1 Hereford population.Keywords: Gene flow, migration, relationship

A combination of multiple trait and repeatability models were used to estimate genetic parameters for birth weight (BW), weaning weight (WW), yearling weight (YW), eighteen month weight (FW) and three measurements of mature weight (MW) using 23 768 records obtained from the South African Brangus Cattle Breed Society. The data covered a period of 7 generations from 1985 to 2010. Direct heritability estimates obtained were 0.21 ± 0.024, 0.23 ± 0.021, 0.22 ± 0.025, 0.29 ± 0.029 and 0.24 ± 0.019 for BW, WW, YW, FW and MW, respectively. Maternal heritability estimates for birth weight and weaning weight were 0.05 ± 0.01 and 0.11 ± 0.001, respectively. The direct genetic correlations between the different traits were all positive, ranging from moderate (0.43 ± 0.081) between YW and MW to high (0.99 ± 0.043) between WW and FW.Keywords: (Co)variance components and ratios, repeatability models, South African Brangus cattle

A study was done to determine which factors had the greatest influence on a heifer’s susceptibility to heat stress. Parameters tested were breed, coat colour, coat score, hide thickness, weight gain, respiration rate and body condition score. The study was conducted in the southeastern Free State. Afrikaner, Bonsmara, Braford, Charolais, Drakensberger and Simmentaler heifers were subjected to a heat tolerance trial. A total of 60 heifers, 10 of each breed were evaluated. Rectal temperature (Tre) was used as a parameter to determine heat stress. The heifers were evaluated on 10 days, at 14:00 during the winter of 2007 and on seventeen days, at 14:00 during the summer of 2007/8 (after 1 h in the sun, no access to shade). In winter a significant difference in rectal temperature Tre between breeds was measured on seven occasions. Phenotypical factors tested for did not affect Tre in winter. In summer significant differences in Tre were measured on 12 occasions between breeds. The following factors had a significant influence on Tre in the following breeds: Afrikaner – hide thickness, Bonsmara – hide thickness, Charolais – coat score.

Economic values of milk volume (VOL), fat yield (FYLD), protein yield (PYLD), live weight (LWT), longevity (LON), calving interval (CIV) and somatic cell score (SCS) were derived for Holstein and Jersey cattle, based on milk payment systems of four major milk buyers in South Africa. The economic value of somatic cell score was calculated for only two of the payment systems. A bio-economic model was used to calculate economic values by determining changes in profit arising from an independent unit increase in each trait. Economic values for VOL, FYLD and PYLD varied substantially among the payment systems; particularly PYLD which ranged from ZAR 7.62/kg to ZAR 21.88/kg. Payment systems that do not pay for milk volume resulted in a negative economic value (-ZAR 0.49/l) for VOL. Live weight and CIV had constant economic values across payment systems (-ZAR 6.62/kg and -ZAR 5.75/day for Holstein and -ZAR 7.49/kg and -ZAR 4.19/day for Jersey, respectively, for LWT and CIV). Economic value of LON varied slightly with payment system (ZAR 1.09/day to ZAR 1.23/day in the Jersey and ZAR 3.59/day to ZAR 3.68/day in the Holstein). The economic value of SCS differed substantially between the two payment systems and was higher in the Holstein (-ZAR 949.26/score and -ZAR 1795.57/score) than in the Jersey (-ZAR 433.87/score and -ZAR 912.90/score). Relative emphasis of traits in the breeding objectives for South African dairy cattle should take due cognisance of the diversity in milk payment systems.

A study was conducted to compare mature cow weight in the South African Simmental population when defined as the weight of the cow at calving or the weight of the cow at weaning of the calf. Data included in the analysis were 14458 records for cow weight at calving (CWT-C) representing 6534 cows and 18871 records for cow weight at weaning (CWT-W) representing 8395 cows. All cows were born between 1968 and 1996, while all calves were born between 1977 and 1998. The following effects had a significant influence on the traits and were included in the genetic analysis: Cow age in years fitted as a covariate term (linear and quadratic) and contemporary group fitted as a fixed effect. Contemporary group was defined as the unique combination of herd, birth year of calf, month of weighing, breeder-defined management group code for the calf and supplementary feeding code for the cow (for CWT-W). All analyses were done using ASREML, first fitting uni-trait and then bi-variate animal models that made provision for up to four weights per cow. The estimated genetic correlation obtained between the two cow weight traits was 0.95 ± 0.03, with a residual correlation of 0.61 ± 0.02. The heritability estimates for CWT-C and CWT-W from this analysis were 0.29 ± 0.04 and 0.37 ± 0.04, respectively. From a breeding perspective, these results confirm that little benefit is to be gained from weighing cows at calving if cows are to be weighed at weaning. If cow weights are to be recorded for an indication of cow maintenance costs, then weight at weaning is the more reliable and practical measure to record. Keywords: Simmental cattle, mature cow weight

h',n: 0.17,0.29,0.14. The results indicate the importance of both permanent maternal environment and herdyear-season by sire interaction in the estimation of the genetic parameters. The exclusion of herd-year-season by sire interaction could lead to a serious overestimation of the direct additive components. The same applies for permanent maternal environment. The exclusion of this factor could lead to a serious overestimation of the maternal components. Both these factors should therefore be included in the across-herd weaning weight analysis of Bonsmara cattle. Speengewig rekords van 24 758 Bonsmarakalwers, die nageslag van 503 bulle uit 30 kuddes gebore vanaf 1980 tot 1993, is gebruik om die invloed van die insluiting van kudde-jaar-seisoen by vaar interaksie op die beraming van die genetiese parameters te ondersoek. Drie aparte modelle is gebruik in die DFREML analise van die data. In die eerste is permanente maternale omgewingseffekte ingesluit as 'n addisionele toevallige effek. Permanente maternale omgewingseffekte is in die tweede model vervang met kudde-jaar-seisoen by vaar interaksie. In die derde model is beide die faktore as addisionele toevallige effekte ingeluit. Die beramings van die (ko)variansie komponente en oorerflikhede vir direk additief (a), maternaal additief (m) en addisionele toevallige effekte vir die drie modelle gebruik in die analise was soos vo^lg: (o2": 138.04,65.23, 67.46; (o2r: 84.77,143.8b, 66.83; (oam: -57.47 , -28.24: -21.97; (o2per ^: 73.72, 71 .01; (o2Hvsrsi 41 .79, 41 .39; (o2": 251 .31',"274.78, 265.97; (o'o: 490.37,497.35,49 0.74;h'^:0.28,0. 13, 0.14;h'^:0.17,0. 29,0.14. Die resultate dui op die belangrikheid van beide die twee addisionele toevallige effekte in die beraming van die genetiese parameters. Die uitsluiting van kudde-jaar-seisoen by vaar interaksie kan lei tot 'n ernstige oorberaming van die direk additiewe komponente. Dieselfde geld vir permanente maternale omgewing. Die uitsluiting van die effek kan weer op sy beurt lei tot 'n oorberaming van die maternaal additiewe komponente, Beide die effekte behoort dus ingesluit te word in

No Abstract.

No Abstract.

No Abstract.

No Abstract.

No Abstract.

To investigate the possibility of a genotype x environment interaction in Bonsmara cattle, a cluster analysis was performed on weaning weight records of 72 811 Bonsmara calves, the progeny of 1 434 sires and 24 186 dams in 35 herds. The following environmental factors were used to classify herds into clusters: solution for herd effects corrected for year-season, sex, age of dam and age at weaning (indicative of the management level in a herd), herd size and average temperature and rainfall. Two different genetic analyses were performed. Breeding values obtained in a univariate analysis were used as basis for comparison to breeding values obtained from a multivariate analysis where weaning weight in each cluster was considered as a separate trait. Direct additive, maternal additive, permanent maternal environment and Herd-Year-Season x Sire (HYSxS) interaction were included as random effects in both analyses. The direct genetic correlations between the clusters varied between 0.51 and 1.00. The low correlation estimates between some of the clusters indicate a possible genotype x environment interaction. Substantial reranking of sires between clusters did occur. However, further research is needed to identify and prioritize variables that can describe the genetics, management and climate of each herd more accurately. Keywords : Bonsmara cattle, Genotype by environment interaction, weaning weight South African Journal of Animal Science Vol. 38 (1) 2008: pp. 51-57

The development of economic selection indices for an integrated Simmentaler production system was described. The breeding objective was defined in terms of production-, functional- and product quality traits. Criteria included in the total index were birth- and weaning weight (direct and maternal), final weight, mature cow weight, days-to-calving, backfat thickness, tenderness and marbling. The total merit index was termed as IT = – 1.60 BWD – 1.95 BWM + 2.23 WWD + 1.75 WWM – 0.54 FW – 2.01 MCW – 13.21 CD + 4.97 BF – 2.36 T + 12.66 M. The correlation between this index and the aggregate breeding objective was 0.988. The economic superiority of the progeny from the top 40% of animals selected on their ranking in the total index, relative to the average progeny, is expected to be R 119.51. South African Journal of Animal Science Vol. 37 (2) 2007: pp. 122-131

Yearling live weight and fleece trait data were obtained from between 2214 and 2270 yearling SA Mutton Merino progeny of the Elsenburg flock during a 20-year period from 1983 to 2002. Information of (co)variances for these traits in SA Mutton Merinos is exceedingly scarce in the literature. Estimates of (co)variance components and ratios were thus obtained from these data, using an Animal Model. Coefficients of variation, for live weight as well as greasy and clean fleece weight were above 18%. Corresponding values for clean yield and fibre diameter were below 9%. Estimates of heritability were 0.23 for yearling live weight, 0.38 for greasy fleece weight, 0.39 for clean fleece weight, 0.59 for clean yield and 0.67 for fibre diameter. Maternal permanent environmental variance ratios were only significant for live weight, greasy fleece weight and clean fleece weight, amounting to 0.09, 0.06 and 0.06, respectively. Genetic correlations between yearling live weight and wool weight were positive but low (0.14 for greasy fleece weight and 0.13 for clean fleece weight). Those of live weight with clean yield and fibre diameter were zero and 0.22, respectively. The genetic correlation between greasy fleece weight and clean fleece weight was 0.87. The genetic correlations of greasy fleece weight with clean yield and fibre diameter were –0.07 and 0.21, respectively. Corresponding correlations with clean fleece weight were 0.43 and 0.38, respectively. The genetic correlation of clean yield with fibre diameter amounted to 0.33. In most cases, the derived values were in agreement with those derived from Merino data sets.

The purpose of this article is to review the development of breeding objectives in beef cattle breeding and the derivation of economic values. There seems to be general consensus that definition of breeding objectives should be the primary step in the design of structured breeding programs. Development of the breeding objective can be described in terms of the following phases: specification of the breeding, production and marketing system, identification of sources of income and expense in commercial herds, determination of biological traits influencing income and expense, derivation of economic values, choice of selection criteria, and estimation of phenotypic and genetic parameters. The modelling methods to derive economic weights can be divided into simulation, dynamic programming and profit functions. Keywords: Beef cattle, Breeding objectives, Economic values South African Journal of Animal Science Vol.33(3) 2003: 142-158

Fitness is of paramount importance to efficient and profitable beef production. Thus, the objective of this study was to estimate genetic components of fitness traits measured in Afrikaner (A), Brahman (B), Charolais (C), Hereford (H) and Simmentaler (S). For this study, the fitness traits recorded were percentage of cows exposed that were subsequently certified pregnant (PR), percentage of certified pregnant cows that subsequently calved (CR), percentage of calves born that survived to weaning (SV) and the percentage of cows exposed that ultimately weaned a calf (WR). Data were mean performance of straightbred, F1 cross, backcross and three-breed cross females. All crossbred females were of at least 25% A heritage. Breed group means were equated with their genetic expectations assuming recombination effects were nil and the heterosis effects were proportional to the expected heterozygosity in the crosses relative to the purebreds. With the exception of B-sired females from CA cross dams, the genetic model fit the breed group means with a high degree of fidelity. Breed-specific genetic effects tended not to individually exceed the magnitude of their standard errors. However, when the breed-specific genetic effects were combined to predict breed group means, the fitness of crossbred females, on average, exceeded that of their straightbred contemporaries. No particular advantage was noted for adding Brahman to the breed composition of crossbred females with at least 25% Afrikaner heritage. In summary, these data are viewed as being supportive of the use of breed resources in organized crossbreeding systems, such as two- and three-breed rotations that maintain at least 25% Afrikaner germplasm in the breeding females. Keywords : Afrikaner cattle genotypes, heterosis effects, predicted phenotypic values, weaning rate

A simulation study was carried out to compare the use of single and composite milk samples for the evaluation of milk composition in dairy cattle. The genetic correlation between the two sampling methods was estimated. Results showed a high genetic correlation between the breeding values arrived from composite and single samples. This indicates that the same genes are possibly responsible for both traits, which makes it possible to use a single sample, instead of a composite sample, in predicting breeding values. South African Journal of Animal Science Vol.32(1) 2002: 44-49

Well-defined breeding objectives form the basis of sound genetic improvement programmes. Breeding objectives for Holstein cattle in South Africa were developed in the current study. Economic values were calculated for those economically relevant traits that had adequate bio-economic data, namely milk volume, fat yield, protein yield, liveweight, longevity, calving interval and somatic cell score (SCS). A bio-economic herd model for pasture-based and concentrate-fed systems in South Africa was used to calculate economic values by determining changes in profit arising from an independent unit increase in each trait. Alternative payment systems were used from four major milk buyers in South Africa. Relative economic values, standardized to the value of protein yield, were used to compare the relative importance of traits. Protein yield and longevity consistently had positive economic values and the converse was true for liveweight and calving interval. Economic value for volume was positive or negative, depending on whether the payment system rewarded or ignored volume. Sensitivity analysis showed that economic values were reasonably robust against fluctuations in the cost of feed and price of beef; with the exception of fat yield, whose value became negative when feed price exceeded ZAR 3.50. Generally, protein yield was the most important trait, although volume, longevity and SCS were more important in some situations. Calving interval was the least important trait, its value ranging from 4% to 22% of protein yield, although the model may have underestimated its value. Further work should focus on facilitating the wide adoption of these breeding objectives by industry.Keywords: Butterfat yield, economic value, liveweight, longevity, milk yield, protein yield, relative economic value, somatic cell score

Somatic cell count (SCC) is of economic importance in dairy production as it directly influences the revenue from the sale of milk. The current study was carried out to determine the economic value of SCC in South African Holstein and Jersey cattle, in order to establish its relative emphasis in breeding objectives. Bulk-tank SCC was calculated from individual cow test-day SCC for 183 Jersey and 209 Holstein herds that participated in the national milk recording scheme in 2012. SCC premium schemes of the two major milk buyers in the country were used, and herds belonged to either a concentrate-fed or pasture-based production system. The economic value of SCC was determined as the simulated change in profit per cow per year, following a 1% increase in individual bulk-tank SCC. Estimated breeding values (EBVs) are based on log10 transformed SCC (somatic cell score, SCS); therefore the final economic value was expressed in South African rand (ZAR) per SCS. Relative economic values, standardized to the value of protein, were used to compare the relative importance of SCS with other objective traits. An increase in SCS by one unit resulted in decreases in profit ranging from ZAR 491.48 to ZAR 1795.57 per cow per year, depending on the breed, production system and payment system. Economic value was nearly double in the Holstein compared with the Jersey, as well as in the concentrate-fed system relative to the pasture-based system. SCS was among the most important traits in the breeding objective, its value ranging from 26% to 118% compared with the most important trait, protein. High relative emphasis should therefore be placed on SCS in breeding objectives for Holstein and Jersey cattle in South Africa. Keywords : Relative economic value; somatic cell score; breeding objectives

Selection for residual feed intake (RFI) as a trait to improve production efficiency was proposed as early as 1963. A low RFI value indicates a more efficient animal and heritability estimates of between 0.28 and 0.58 have been reported for RFI in the literature. It is also reported that a 13.38 g/d reduction in methane emission was associated with a 1 kg/d reduction in the Estimated Breeding Value (EBV) for RFI, with low-RFI steers emitting 25% less methane daily. The difference in methane production in high and low RFI animals cannot be explained by the difference in feed intake alone. Possible reasons could be digestion of feed, protein turnover and overall tissue metabolism (mitochondrial function, body composition, Insulin Growth Factor-I (IGF-I) and cortisol levels), activity, thermoregulation and growth. Low-RFI animals tend to digest feed better than high-RFI animals, and as intake increases there is a tendency for digestion to decrease. The correlation between RFI and dry matter (DM) digestibility has been determined to be r = –0.33. A positive correlation exists between metabolisable energy for maintenance (ME) and RFI, as well as between ME and protein turnover. Thus protein secretion in low-RFI animals are the same as high-RFI animals, but the breakdown of protein in low-RFI animals is less. Clear differences can be observed in heat production, with low-RFI animals producing up to 21% less heat than high-RFI animals. Selection for low-RFI animals may thus reduce the carbon footprint of beef cattle. Keywords: Body composition, production efficiency, carbon footprint, protein turnover, selection indices, methane emission

A simulation study was carried out to investigate the effect of selection on the estimation of genetic parameters for butterfat production in dairy cattle. It was found that selection leads to a substantial overestimation of fixed effects and variance components and an underestimation of heritability estimates. This effect was attributed to the fact that all information on all animals in the analysis should be available to compensate for the effect of selection. (South African Journal of Animal Science, 2001, 31(2): 107-114)

Selection for production and reproduction in South African Merino sheep is always combined with selection based on visual appraisal and will, in all probability, remain so for many years to come. Heritabilities for acceptability were estimated using a threshold model to analyse data from two parent Merino studs. Effects included in the analysis were sex, birth status, age of dam and year of birth. An acceptable animal was defined as one that was present in the stud at 18 months of age, implying that such an animal would either be retained or sold for breeding purposes. This provided one threshold and two classes (acceptable or not acceptable). Records from the two studs used comprised 3011 progeny of 31 sires and 6495 progeny of 70 sires. Error variance was taken as unity and heritability estimated as h2 = 4s 2s / 1 + s2s where s 2s is the sire variance. Heritability estimates were 0.210 and 0.448. The results suggest that selection improvement for acceptability is possible, and that breeding values for this trait should be supplied for AI sires. (South African Journal of Animal Science, 2001, 31(1): 13-14)

Data from a multibreed composite beef cattle population, managed under intensive irrigated grazing conditions,were used to estimate direct additive heritabilities (h2a), maternal heritabilities (h2m) and maternal permanent environmental effects (c2) for birth weight (BW) and weaning weight (WW) of the calf and cow efficiency of the dam (CE: WW/dam weight0.75 x 100). Calves born between 1968 and 1993 (n = 52628) had varying levels of Hereford genes, ranging from 0% to 100%, with an average of 19.3%. Direct heritabilities, fitting unitrait models, were 0.72, 0.54 and 0.19 for BW, WW and CE, respectively, with corresponding estimates of maternal heritabilities being 0.14, 0.21 and 0.42. Genetic correlations between direct and maternal effects (ram) were negative for all three traits, varying from -0.40 to -0.65. Maternal permanent environmental effects were 0.06, 0.12 and 0.11 for BW, WW and CE, respectively. Direct breeding values and maternal breeding values for BW and WW decreased with increasing proportion of Hereford. Direct breeding value for CE increased, while maternal breeding value for CE reached a minimum value at 0.62 proportion of Hereford. (South African Journal of Animal Science, 2000, 30(3): 220-229)

Genetic parameters were estimated for 36-, 42-, 50-, 100- and 150-day weight in the South African Mutton Merino breed. The direct heritability estimates obtained were 0.270, 0.366, 0.278, 0.185 and 0.115 respectively. The maternal heritability estimates for the respective weights were 0.494, 0.249, 0.129, 0.091 and 0.080. The correlation between the animal effects (direct and maternal) varied between -1.000 for 36-day weight to -0.376 for 150-day weight. Very little selection progress was made over the period (1980-1999) in the breed. (South African Journal of Animal Science, 2000, 30(3): 172-177)

Data from purebred and crossbred cattle, consisting of the Afrikaner (A), Simmentaler (S) and Hereford (H) breeds managed in a relatively intensive but high stocking rate environment, were analysed to estimate breed direct effects, individual heterotic effects, breed maternal and maternal heterotic effects for birth weight (BW) and weaning weight (WW). Simmentaler breed direct effects, expressed as deviation from the general mean, were positive (P < 0.01) for both traits. Hereford and Afrikaner breed direct effects were negative (P < 0.01) for both traits while the Afrikaner breed direct effects exceeded those of the Hereford. Afrikaner direct maternal effects were positive (P < 0.01) for both traits. The Hereford direct maternal effect was negative (P < 0.05) (-2.9%) for WW. Simmentaler maternal effect was negative (P < 0.01 ) for BW but non-significant (P > 0.05) for WW. Individual heterotic effects for BW were significant (P < 0.01) in H x S (3.5%) and S x A (11.0%) only. Individual heterotic effects were positive (P < 0.01) for WW, with that of the H x A (9.8%) and S x A (6.7%) crosses exceeding the S x H (3.1%) cross. Maternal heterotic effects were non-significant (P > 0.05) for both BW and WW. (South African Journal of Animal Science, 2000, 30(3): 193-203)

Known environmental effects influencing type trait scores in South African Jersey cattle were identified. Variance components and heritabilities were estimated for these traits as well as genetic correlations among them and with production traits. Heritability estimates were generally low to medium. It is suggested that hoof and leg traits be excluded due to low estimated heritabilities and/or coefficients of variation. Genetic correlation estimates suggested that selection for production yield should improve most type traits and vice versa. Estimation of breeding values and fitting a multiple trait model is suggested. (South African Journal of Animal Science, 2000, 30(3): 186-192)

(South African J of Animal Science, 2000, 30, Supplement 1: 99-101)

(South African J of Animal Science, 2000, 30, Supplement 1: 102-104)

Extracted from text ... Genetic trends for growth in the Gudali and Wakwa cattle breeds of CameroonA.L. Ebangi,#G.J. Erasmus, F.W.C. Neser and C.L. TawahDept of Animal Science, University of the Orange Free State, PO Box 339,Bloemfontein 9300# Email :Gert@landbou.uovs.ac.zaIntroductionCattle production in Cameroon is essentially conducted by a traditional small-scale husbandry management system.The resultant effects are high inbreeding, low fertility, high mortalities of about 5 to 10% in adult cattle and about 20% incalves. In an effort to improve the situation, the government has put in place a number of programmes for cattle productionimprovement. In 1952 a programme code-named ?Wakwa? was initiated (Mandon, 1957). This ..

Extracted from text ... Crossbreeding Holstein-Friesian with Ethiopian Boran cattle in a tropical highlandenvironment: preliminary estimates of additive and heterotic effects on milkproduction traitsS. Demeke 1# , F.W.C. Neser 1 , S.J. Schoeman 2 , G.J. Erasmus 1 , J.B.Van Wyk 1 , and A. Gebrewolde 31 Department of Animal Science, University of the Orange Free State, P.O. Box 339, Bloemfontein, 9300, Republic of SouthAfrica; 2 Department of Animal Sciences, University of Stellenbosch, Private Bag XI, 7602 Matieland, Republic of SouthAfrica; 3 Ethiopian Agricultural Research Organization, P.O.Box 2003, Addis Ababa, Ethiopia# e-mail: sendros@landbou.uovs.ac.zaIntroductionThe Boran cattle breed is a zebu type that originated in the ..

A breed characterisation study on Horro hair sheep (for description see Galal, 1983) has been underway at Bako Research Centre in Ethiopia since 1977. In this paper the results of analysis of early growth performance, survival and litter size are presented.