Michiel Scholtz - Academia.edu (original) (raw)

Papers by Michiel Scholtz

Research paper thumbnail of The likely efficiency of prenatal energy utilization

South African Journal Of Animal Science

Research paper thumbnail of Genetic diversity in selected stud and commercial herds of the Afrikaner cattle breed

South African Journal of Animal Science

The Afrikaner is one of three indigenous cattle breeds found in South Africa. Afrikaner cattle we... more 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 variatio...

Research paper thumbnail of Estimates of variance components for feedlot traits of the Simmentaler breed in South Africa

South African Journal of Animal Science

Breeding of beef cattle is changing, with more emphasis on efficiency of production. Feed cost is... more 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...

Research paper thumbnail of Research and development on climate change and greenhouse gases in support of climate-smart livestock production and a vibrant industry

South African Journal of Animal Science, 2015

Climate change represents a feedback-loop in which livestock production both contributes to the p... more Climate change represents a feedback-loop in which livestock production both contributes to the problem and suffers from the consequences. The impact of global warming and continued, uncontrolled release of greenhouse gasses (GHG) has twofold implications for the livestock industry, and consequently food security. Firstly, the continuous increase in ambient temperature is predicted to have a direct effect on the animal, as well as on food and nutrition security, due to changes associated with temperature itself, relative humidity, rainfall distribution in time and space, altered disease distribution, changes in the ecosystem and biome composition. Secondly, the responsibility of livestock production is to limit the release of greenhouse gases (GHG) or the carbon footprint, in order to ensure future sustainability. This can be done by implementing new or adapted climate-smart production systems, the use of known and new technologies to turn waste into assets, and by promoting sustain...

Research paper thumbnail of Methane production in different breeds, grazing different pastures or fed a total mixed ration, as measured by a Laser Methane Detector

South African Journal of Animal Science, 2015

Agriculture is responsible for 5% to 10% of the global anthropogenic greenhouse gas (GHG) emissio... more 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 secon...

Research paper thumbnail of Evaluation of cytoplasmic genetic effects for production and reproduction traits in Afrikaner cattle

South African Journal of Animal Science, 2014

The influence of cytoplasmic effects on weaning weight (WW) and age at first calving (AFC) were i... more The influence of cytoplasmic effects on weaning weight (WW) and age at first calving (AFC) were investigated in the South African Afrikaner beef breed. A total of 14 535 AFC records (1974 - 2008) and 68 152 WW records (1974 - 2011) were used in the estimation of variance components. All cows were assigned to different damlines, using the pedigree information available. The model used for WW include direct additive, maternal additive, the covariance between the animal-, permanent maternal environmental-, herdyear-season x sire- and damline effects, while the simplest model which include only direct- and damline effects were used for AFC. The contribution of the cytoplasmic effects to the total variance was negligible (less than 0.5%) for both traits. These results suggest that cytoplasmic effects can be ignored in genetic evaluations of Afrikaner cattle for the traits investigated.

Research paper thumbnail of Genetic variability and relationships among nine southern African and exotic cattle breeds

An existing 11 microsatellite marker database that resulted from parentage verification in respon... more An existing 11 microsatellite marker database that resulted from parentage verification in response to requests from industry, was used to assess genetic diversity among nine breeds of cattle. These breeds were drawn from B. indicus (Boran (BOR) and Brahman (BRA)), B. taurus (Angus (ANG) and Simmental (SIM)), and B. taurus africanus (Afrikaner (AFR), Bonsmara (BON), Drakensberger (DRA), Nguni (NGU), and Tuli (TUL)). Due to the cost of genotyping, genetic diversity studies using SNPs rely on relatively low numbers of animals to represent each of the breeds. Large numbers of animals have been genotyped for parentage verification using microsatellite markers, therefore, the microsatellite information on large numbers of animals has the potential to provide more accurate estimates of genomic diversity. A minimum of 300 animals were randomly chosen from each breed and were used to assess withinand between breed genetic diversity. All breeds had high levels of heterozygosity and minimal i...

Research paper thumbnail of Challenges for Beef Production in Developing Countries of Southern Africa

One potential consequence of significant and permanent changes to the climate is altered patterns... more One potential consequence of significant and permanent changes to the climate is altered patterns of diseases in animals. This may include (a) the emergence of new disease syndromes and (b) a change in the prevalence of existing diseases, particularly those spread by biting insects. Therefore animals will be exposed to different parasites and diseases as indicated from the predicted change in the distribution of, for example, Tsetse in Africa; putting an even greater pressure on production and the survival of livestock breeds. The OIE Scientific Commission has concluded that climatic changes are likely to be a factor in determining the spread of some diseases, especially those that are vector-borne. The two most mentioned emerging and reemerging cattle diseases in a recent OIE survey were Bluetongue and Rift Valley fever.

Research paper thumbnail of A case-control study to identify a genetic component contributing to wet carcass syndrome in sheep

Wet carcass syndrome (WCS) is a condition predominantly found in lambs which negatively affects t... more Wet carcass syndrome (WCS) is a condition predominantly found in lambs which negatively affects the quality of carcasses. During the pre-slaughter period, the animal appears to be clinically normal, showing no symptoms of an abnormality. However, after slaughter and removal of the skin the carcass appears to be “wet”. The condition is described phenotypically as a subcutaneous accumulation of watery fluid. Therefore, the objective of this investigation was to scan the genomes of afflicted and unafflicted lambs in search of putative quantitative trait loci associated with the WCS phenotype in sheep. Muscle samples from lamb carcasses (43 afflicted and 41 unafflicted) were collected from three different slaughterhouses in the Northern Cape Province of South Africa and Southern Namibia. To test for an association between the phenotype (WCS) and an autosomal genetic marker, a case-control study design was implemented. Separate analyses for each sex were motivated by individual SNP on th...

Research paper thumbnail of Maximum herd efficiency in meat production IV. Crossbred reproduction and constant slaughter mass

South African Journal of Animal Science, 1992

Higher reproduction and lower replacement rates lead to a higher proportion of terminally crossbr... more Higher reproduction and lower replacement rates lead to a higher proportion of terminally crossbred offspring to sell. Substantial improvement in herd efficiency can be achieved by improvement in the ratio of replacement rate to reproduction rate by selection or crossbreeding. In crossbreeding for surplus reproduction, reproduction from F1 dams may do better than rotational crossbreeding, especially in pigs. Evidence is presented that a strong enough maternal limitation on offspring size sometimes exists in small enough dams in primiparous animals so that fetal dystocia can be avoided. With a constant slaughter mass, a decreas,~ in breeder limit mass or an increase in feeder limit mass will lead to gain in herd efficiency; if, furthermore, an Jptimal or maximal feeder-breeder limit mass ratio exists, an optimal feeder limit mass can be calculated for the ml1J(imization of herd efficiency. .

Research paper thumbnail of A balanced perspective on the importance of extensive ruminant production for human nutrition and livelihoods and its contribution to greenhouse gas emissions

South African Journal of Science, 2020

There is a general perception that ruminants produce large quantities of greenhouse gases which c... more There is a general perception that ruminants produce large quantities of greenhouse gases which contribute to global warming. Sometimes percentages are quoted out of context. For example, the percentage quoted for developed countries indicates the greenhouse gas contribution from livestock is less than 6%, while that for developing countries is 40–50%. However, the reason for this relatively low contribution from developed countries is because of very high contributions from other sectors. Ruminant production also is in the spotlight as it is the world’s largest user of land and South Africa is no exception. Only ruminants can utilise areas of non-arable land where the vegetation is rich in fibre and convert this fibre into high-quality nutrients for human consumption. Foods from animal sources (including ruminants) are essential for the human diet, as they support early childhood and cognitive development. Many rural households depend on ruminants and these animals are central to t...

Research paper thumbnail of Evaluasie van bestaande seleksiekriteria vir beeste in terme van totale kuddedoeltreffendheid

Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie, 1991

Breeding should always be aimed at the improvement of total herd efficiency. Selection criteria w... more Breeding should always be aimed at the improvement of total herd efficiency. Selection criteria were evaluated from this viewpoint. In dairy cattle there was a marked increase in production traits in the 10 year period studied. During this period calving interval was also shortened by 5%. It was indicated that these changes probably led to an improvement in total herd efficiency. Thus, it seems that performance testing and selection criteria are utilized in the correct manner by dairy cattle breeders. In beef cattle no improvement was found in performance under farming conditions.

Research paper thumbnail of Genetic variability and relationships in nine South African cattle breeds using microsatellite markers

Tropical Animal Health and Production, 2019

Research paper thumbnail of Genetic diversity of Afrikaner cattle in southern Africa

Tropical animal health and production, Jan 18, 2017

The Afrikaner is an indigenous South African breed of "Sanga" type beef cattle along wi... more The Afrikaner is an indigenous South African breed of "Sanga" type beef cattle along with breeds such as the Drakensberger and Nguni. Six composite breeds have been developed from crosses with the Afrikaner. Additionally, Afrikaner has been the base from which exotic breeds were established in South Africa through backcrossing. The study examined genetic diversity of Afrikaner cattle by genotyping 1257 animals from 27 herds in different geographic areas of South Africa and Namibia using 11 microsatellite markers. Multiple-locus assignment, performed using the Bayesian clustering algorithm of STRUCTURE, revealed three underlying genotypic groups. These groups were not geographically localized. Across herds and markers, the proportion of unbiased heterozygosity ranged from 0.49 to 0.72 averaging 0.57; mean number of alleles per locus ranged from 3.18 to 7.09, averaging 4.81; and allelic richness ranged from 2.35 to 3.38, averaging 2.67. It is concluded that a low inbreeding ...

Research paper thumbnail of The use of indigenous cattle in terminal cross-breeding to improve beef cattle production in Sub-Saharan Africa

Animal Genetic Resources/Ressources génétiques animales/Recursos genéticos animales, 2010

Research paper thumbnail of The effect of environmental factors and husbandry practices on stress in goats

Small Ruminant Research, 2016

Research paper thumbnail of Alternative approaches to evaluation of cow efficiency

South African Journal of Animal Science, 2017

Research paper thumbnail of Insight into the genetic composition of South African Sanga cattle using SNP data from cattle breeds worldwide

Genetics, selection, evolution : GSE, Nov 15, 2016

Understanding the history of cattle breeds is important because it provides the basis for develop... more Understanding the history of cattle breeds is important because it provides the basis for developing appropriate selection and breed improvement programs. In this study, patterns of ancestry and admixture in Afrikaner, Nguni, Drakensberger and Bonsmara cattle of South Africa were investigated. We used 50 K single nucleotide polymorphism genotypes that were previously generated for the Afrikaner (n = 36), Nguni (n = 50), Drakensberger (n = 47) and Bonsmara (n = 44) breeds, and for 394 reference animals representing European taurine, African taurine, African zebu and Bos indicus. Our findings support previous conclusions that Sanga cattle breeds are composites between African taurine and Bos indicus. Among these breeds, the Afrikaner breed has significantly diverged from its ancestral forebears, probably due to genetic drift and selection to meet breeding objectives of the breed society that enable registration. The Nguni, Drakensberger and Bonsmara breeds are admixed, perhaps uninten...

Research paper thumbnail of Livestock and climate change - a balanced perspective : consumer savvy

The South African Society for Animal Science (SASAS) recognises the effect of livestock on greenh... more The South African Society for Animal Science (SASAS) recognises the effect of livestock on greenhouse gas (GHG) production and climate change, and believes it is important that through research, methods are developed and put in place to mitigate this effect. Livestock industries should also recognise the effect of livestock on climate change and actively support strategies to mitigate it.

Research paper thumbnail of Did Genetic Change Improve Production Efficiency in Three Landrace Breeds of South Africa?

Abstract Text: It is easy to achieve genetic change, but much more difficult to achieve genetic i... more Abstract Text: It is easy to achieve genetic change, but much more difficult to achieve genetic improvement.This study investigates the influence of selection on the cow efficiency in three landrace beef breeds (Afrikaner,Bonsmara,Nguni) in South Africa over a period of 25 years.Cow efficiency was defined as kilogram calf weaned (KgC) per cow Large Stock Unit (LSU). Breeding values for direct weaning weight in the Afrikaner and Bonsmara changed by +6.7kg and +11.7kg, respectively.That for mature cow weight only changed in the case of the Bonsmara (+9kg).The phenotypic changes were +21kg, +15kg and -14kg for weaning weight; and +14kg, +16kg and -22kg for mature cow weight in the Afrikaner, Bonsmara and Nguni, respectively.Cow efficiency increased by 12.0% in the Afrikaner and by 2.7% in the Bonsmara and decreased by 7.3% in the Nguni. Possible reasons for the differences between the breeds are discussed. Keywords: large stock unit production trends weaning weight

Research paper thumbnail of The likely efficiency of prenatal energy utilization

South African Journal Of Animal Science

Research paper thumbnail of Genetic diversity in selected stud and commercial herds of the Afrikaner cattle breed

South African Journal of Animal Science

The Afrikaner is one of three indigenous cattle breeds found in South Africa. Afrikaner cattle we... more 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 variatio...

Research paper thumbnail of Estimates of variance components for feedlot traits of the Simmentaler breed in South Africa

South African Journal of Animal Science

Breeding of beef cattle is changing, with more emphasis on efficiency of production. Feed cost is... more 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...

Research paper thumbnail of Research and development on climate change and greenhouse gases in support of climate-smart livestock production and a vibrant industry

South African Journal of Animal Science, 2015

Climate change represents a feedback-loop in which livestock production both contributes to the p... more Climate change represents a feedback-loop in which livestock production both contributes to the problem and suffers from the consequences. The impact of global warming and continued, uncontrolled release of greenhouse gasses (GHG) has twofold implications for the livestock industry, and consequently food security. Firstly, the continuous increase in ambient temperature is predicted to have a direct effect on the animal, as well as on food and nutrition security, due to changes associated with temperature itself, relative humidity, rainfall distribution in time and space, altered disease distribution, changes in the ecosystem and biome composition. Secondly, the responsibility of livestock production is to limit the release of greenhouse gases (GHG) or the carbon footprint, in order to ensure future sustainability. This can be done by implementing new or adapted climate-smart production systems, the use of known and new technologies to turn waste into assets, and by promoting sustain...

Research paper thumbnail of Methane production in different breeds, grazing different pastures or fed a total mixed ration, as measured by a Laser Methane Detector

South African Journal of Animal Science, 2015

Agriculture is responsible for 5% to 10% of the global anthropogenic greenhouse gas (GHG) emissio... more 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 secon...

Research paper thumbnail of Evaluation of cytoplasmic genetic effects for production and reproduction traits in Afrikaner cattle

South African Journal of Animal Science, 2014

The influence of cytoplasmic effects on weaning weight (WW) and age at first calving (AFC) were i... more The influence of cytoplasmic effects on weaning weight (WW) and age at first calving (AFC) were investigated in the South African Afrikaner beef breed. A total of 14 535 AFC records (1974 - 2008) and 68 152 WW records (1974 - 2011) were used in the estimation of variance components. All cows were assigned to different damlines, using the pedigree information available. The model used for WW include direct additive, maternal additive, the covariance between the animal-, permanent maternal environmental-, herdyear-season x sire- and damline effects, while the simplest model which include only direct- and damline effects were used for AFC. The contribution of the cytoplasmic effects to the total variance was negligible (less than 0.5%) for both traits. These results suggest that cytoplasmic effects can be ignored in genetic evaluations of Afrikaner cattle for the traits investigated.

Research paper thumbnail of Genetic variability and relationships among nine southern African and exotic cattle breeds

An existing 11 microsatellite marker database that resulted from parentage verification in respon... more An existing 11 microsatellite marker database that resulted from parentage verification in response to requests from industry, was used to assess genetic diversity among nine breeds of cattle. These breeds were drawn from B. indicus (Boran (BOR) and Brahman (BRA)), B. taurus (Angus (ANG) and Simmental (SIM)), and B. taurus africanus (Afrikaner (AFR), Bonsmara (BON), Drakensberger (DRA), Nguni (NGU), and Tuli (TUL)). Due to the cost of genotyping, genetic diversity studies using SNPs rely on relatively low numbers of animals to represent each of the breeds. Large numbers of animals have been genotyped for parentage verification using microsatellite markers, therefore, the microsatellite information on large numbers of animals has the potential to provide more accurate estimates of genomic diversity. A minimum of 300 animals were randomly chosen from each breed and were used to assess withinand between breed genetic diversity. All breeds had high levels of heterozygosity and minimal i...

Research paper thumbnail of Challenges for Beef Production in Developing Countries of Southern Africa

One potential consequence of significant and permanent changes to the climate is altered patterns... more One potential consequence of significant and permanent changes to the climate is altered patterns of diseases in animals. This may include (a) the emergence of new disease syndromes and (b) a change in the prevalence of existing diseases, particularly those spread by biting insects. Therefore animals will be exposed to different parasites and diseases as indicated from the predicted change in the distribution of, for example, Tsetse in Africa; putting an even greater pressure on production and the survival of livestock breeds. The OIE Scientific Commission has concluded that climatic changes are likely to be a factor in determining the spread of some diseases, especially those that are vector-borne. The two most mentioned emerging and reemerging cattle diseases in a recent OIE survey were Bluetongue and Rift Valley fever.

Research paper thumbnail of A case-control study to identify a genetic component contributing to wet carcass syndrome in sheep

Wet carcass syndrome (WCS) is a condition predominantly found in lambs which negatively affects t... more Wet carcass syndrome (WCS) is a condition predominantly found in lambs which negatively affects the quality of carcasses. During the pre-slaughter period, the animal appears to be clinically normal, showing no symptoms of an abnormality. However, after slaughter and removal of the skin the carcass appears to be “wet”. The condition is described phenotypically as a subcutaneous accumulation of watery fluid. Therefore, the objective of this investigation was to scan the genomes of afflicted and unafflicted lambs in search of putative quantitative trait loci associated with the WCS phenotype in sheep. Muscle samples from lamb carcasses (43 afflicted and 41 unafflicted) were collected from three different slaughterhouses in the Northern Cape Province of South Africa and Southern Namibia. To test for an association between the phenotype (WCS) and an autosomal genetic marker, a case-control study design was implemented. Separate analyses for each sex were motivated by individual SNP on th...

Research paper thumbnail of Maximum herd efficiency in meat production IV. Crossbred reproduction and constant slaughter mass

South African Journal of Animal Science, 1992

Higher reproduction and lower replacement rates lead to a higher proportion of terminally crossbr... more Higher reproduction and lower replacement rates lead to a higher proportion of terminally crossbred offspring to sell. Substantial improvement in herd efficiency can be achieved by improvement in the ratio of replacement rate to reproduction rate by selection or crossbreeding. In crossbreeding for surplus reproduction, reproduction from F1 dams may do better than rotational crossbreeding, especially in pigs. Evidence is presented that a strong enough maternal limitation on offspring size sometimes exists in small enough dams in primiparous animals so that fetal dystocia can be avoided. With a constant slaughter mass, a decreas,~ in breeder limit mass or an increase in feeder limit mass will lead to gain in herd efficiency; if, furthermore, an Jptimal or maximal feeder-breeder limit mass ratio exists, an optimal feeder limit mass can be calculated for the ml1J(imization of herd efficiency. .

Research paper thumbnail of A balanced perspective on the importance of extensive ruminant production for human nutrition and livelihoods and its contribution to greenhouse gas emissions

South African Journal of Science, 2020

There is a general perception that ruminants produce large quantities of greenhouse gases which c... more There is a general perception that ruminants produce large quantities of greenhouse gases which contribute to global warming. Sometimes percentages are quoted out of context. For example, the percentage quoted for developed countries indicates the greenhouse gas contribution from livestock is less than 6%, while that for developing countries is 40–50%. However, the reason for this relatively low contribution from developed countries is because of very high contributions from other sectors. Ruminant production also is in the spotlight as it is the world’s largest user of land and South Africa is no exception. Only ruminants can utilise areas of non-arable land where the vegetation is rich in fibre and convert this fibre into high-quality nutrients for human consumption. Foods from animal sources (including ruminants) are essential for the human diet, as they support early childhood and cognitive development. Many rural households depend on ruminants and these animals are central to t...

Research paper thumbnail of Evaluasie van bestaande seleksiekriteria vir beeste in terme van totale kuddedoeltreffendheid

Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie, 1991

Breeding should always be aimed at the improvement of total herd efficiency. Selection criteria w... more Breeding should always be aimed at the improvement of total herd efficiency. Selection criteria were evaluated from this viewpoint. In dairy cattle there was a marked increase in production traits in the 10 year period studied. During this period calving interval was also shortened by 5%. It was indicated that these changes probably led to an improvement in total herd efficiency. Thus, it seems that performance testing and selection criteria are utilized in the correct manner by dairy cattle breeders. In beef cattle no improvement was found in performance under farming conditions.

Research paper thumbnail of Genetic variability and relationships in nine South African cattle breeds using microsatellite markers

Tropical Animal Health and Production, 2019

Research paper thumbnail of Genetic diversity of Afrikaner cattle in southern Africa

Tropical animal health and production, Jan 18, 2017

The Afrikaner is an indigenous South African breed of "Sanga" type beef cattle along wi... more The Afrikaner is an indigenous South African breed of "Sanga" type beef cattle along with breeds such as the Drakensberger and Nguni. Six composite breeds have been developed from crosses with the Afrikaner. Additionally, Afrikaner has been the base from which exotic breeds were established in South Africa through backcrossing. The study examined genetic diversity of Afrikaner cattle by genotyping 1257 animals from 27 herds in different geographic areas of South Africa and Namibia using 11 microsatellite markers. Multiple-locus assignment, performed using the Bayesian clustering algorithm of STRUCTURE, revealed three underlying genotypic groups. These groups were not geographically localized. Across herds and markers, the proportion of unbiased heterozygosity ranged from 0.49 to 0.72 averaging 0.57; mean number of alleles per locus ranged from 3.18 to 7.09, averaging 4.81; and allelic richness ranged from 2.35 to 3.38, averaging 2.67. It is concluded that a low inbreeding ...

Research paper thumbnail of The use of indigenous cattle in terminal cross-breeding to improve beef cattle production in Sub-Saharan Africa

Animal Genetic Resources/Ressources génétiques animales/Recursos genéticos animales, 2010

Research paper thumbnail of The effect of environmental factors and husbandry practices on stress in goats

Small Ruminant Research, 2016

Research paper thumbnail of Alternative approaches to evaluation of cow efficiency

South African Journal of Animal Science, 2017

Research paper thumbnail of Insight into the genetic composition of South African Sanga cattle using SNP data from cattle breeds worldwide

Genetics, selection, evolution : GSE, Nov 15, 2016

Understanding the history of cattle breeds is important because it provides the basis for develop... more Understanding the history of cattle breeds is important because it provides the basis for developing appropriate selection and breed improvement programs. In this study, patterns of ancestry and admixture in Afrikaner, Nguni, Drakensberger and Bonsmara cattle of South Africa were investigated. We used 50 K single nucleotide polymorphism genotypes that were previously generated for the Afrikaner (n = 36), Nguni (n = 50), Drakensberger (n = 47) and Bonsmara (n = 44) breeds, and for 394 reference animals representing European taurine, African taurine, African zebu and Bos indicus. Our findings support previous conclusions that Sanga cattle breeds are composites between African taurine and Bos indicus. Among these breeds, the Afrikaner breed has significantly diverged from its ancestral forebears, probably due to genetic drift and selection to meet breeding objectives of the breed society that enable registration. The Nguni, Drakensberger and Bonsmara breeds are admixed, perhaps uninten...

Research paper thumbnail of Livestock and climate change - a balanced perspective : consumer savvy

The South African Society for Animal Science (SASAS) recognises the effect of livestock on greenh... more The South African Society for Animal Science (SASAS) recognises the effect of livestock on greenhouse gas (GHG) production and climate change, and believes it is important that through research, methods are developed and put in place to mitigate this effect. Livestock industries should also recognise the effect of livestock on climate change and actively support strategies to mitigate it.

Research paper thumbnail of Did Genetic Change Improve Production Efficiency in Three Landrace Breeds of South Africa?

Abstract Text: It is easy to achieve genetic change, but much more difficult to achieve genetic i... more Abstract Text: It is easy to achieve genetic change, but much more difficult to achieve genetic improvement.This study investigates the influence of selection on the cow efficiency in three landrace beef breeds (Afrikaner,Bonsmara,Nguni) in South Africa over a period of 25 years.Cow efficiency was defined as kilogram calf weaned (KgC) per cow Large Stock Unit (LSU). Breeding values for direct weaning weight in the Afrikaner and Bonsmara changed by +6.7kg and +11.7kg, respectively.That for mature cow weight only changed in the case of the Bonsmara (+9kg).The phenotypic changes were +21kg, +15kg and -14kg for weaning weight; and +14kg, +16kg and -22kg for mature cow weight in the Afrikaner, Bonsmara and Nguni, respectively.Cow efficiency increased by 12.0% in the Afrikaner and by 2.7% in the Bonsmara and decreased by 7.3% in the Nguni. Possible reasons for the differences between the breeds are discussed. Keywords: large stock unit production trends weaning weight