Content: Since hundreds of years, tanners share the opinion that hides from different cattle breeds lead to varying leather qualities. Especially European hides from the alpine region (e. g. Simmentaler or brown origin) are preferred by tanners. These leathers feature a higher thickness, a maximum utilisation induced by a minor thickness difference over the whole area and a lower tensile strength in contrast to leathers from other breeds. However, are these alpine hides better because of their breed affiliation or because they are kept in special regional conditions? It is known that, besides the breed, also other factors can influence the rawhide and leather quality like age, gender, nutrition and climate conditions. In addition, present dairy and beef cattle are high-performance cattle by breeding, which leads to more crossbreeds than 100 years ago. Our intention was to find out, whether leather quality nowadays is still a function of breed or not. For that purpose, 40 rawhides from four different cattle breeds (Angus, Charolais, Simmentaler, Limousin) were collected from the Saxon region. From each breed, five male and five female rawhides were collected. The age of each individual was restricted to two years. All 40 rawhides were tanned with the same technology for furniture leather. Leather quality was characterized by determining chemical and physical parameters. Chemical parameters included collagen content, fat content and ignition lost (DIN 181218). The physical parameters were tensile strength (DIN EN ISO 3376), elongation at break (DIN EN ISO 3376) and stitch tear resistance (DIN EN ISO 23910). The analyses revealed that the chemical parameters were identical for all examined breeds. For this reason, the chemical composition of a cattle skin is irrespective of breed origin. The tensile strength of the leathers showed only a small significant difference between Angus and Limousin (p= 0.05). Leathers from Limousin hides showed significantly different elongations at break compared to Angus, Charolais and Simmentaler. The stitch tear resistance varied in nearly all breeds. Significant differences were detected between all breeds except between Angus and Charolais as well as Angus and Simmentaler. Plotting the measured physical values against gender or age of the individuals showed no correlation. In summary, only minor differences between the cattle breeds were found. But this tendency must be confirmed by a larger quantity of test individuals. For this purpose, an analysis is planed with 100 individuals from different breeds and crossbreeds. Take-Away: Many tanners share the opinion that hides from different attle breeds lead to varying leather qualities. We found only minor differences of the physical parameters between the cattle breeds with a random sample of 10 individuals per breed. To confirm this tendency, an analysis is planed with 100 individuals from different breeds and crossbreeds.

Thesis (MScAgric)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The aim of this study was to provide scientifically founded guidelines to enhance the understanding of beef production from natural pastures in arid sweet veld regions. Cattle from four breed types ranging from large to small frame sizes (Simmentaler cross > Bonsmara cross > Afrikaner > Nguni) were compared in terms of cow production and efficiency as well as the growth performance, carcass and meat quality of steers slaughtered at 18, 24 and 30 months of age. Eighteen and 30 month old steers were slaughtered at the end of the wet summer season, while the 24 month old steers were slaughtered at the end of the dry winter season. The Afrikaner herd (59.8 ± 9.0 %) had lower (p < 0.05) pregnancy rates than the Simmentaler cross (79.3 ± 12.2 %), Bonsmara cross (76.5 ± 11.1 %) and Nguni herds (86.1 ± 5.8 %). Breed differences (p < 0.05) for weaning weight and preweaning gain were observed (Simmentaler cross > Bonsmara cross > Afrikaner > Nguni). The Nguni cow herd (46.5 ± 5.7 kg/100 kg mated) was more (p < 0.05) efficient than the Simmentaler cross (36.2 ± 5.5 kg/100 kg mated), Bonsmara cross (37.7 kg/100 kg mated) and Afrikaner herds (29.5 ± 5.9 kg/100 kg mated). During the dry winter season steers gained 23.4 ± 1.5 kg from 7 to 12 months of age and from 18 to 24 months of age they gained 20.9 ± 2.0 kg. During the wet summer season steers gained 109.7 ± 1.8 kg from 12 to 18 months and 120.3 ± 4.1 kg from 24 to 30 months of age. The best (p > 0.05) fat classification codes were attained at 30 months of age and the worst (p < 0.05) at 24 months of age. Simmentaler cross steers attained the lowest (p < 0.05) fat classification at all three age classes. At 30 months of age, 15 of the 63 steers slaughtered had 3 or 4 permanent incisors, while 47 steers had 2 permanent incisors. The total amount as well as the percentage kidney and omental fat were the highest (p < 0.05) at 30 months of age and the lowest (p < 0.05) at 24 months. Back fat thickness followed the same pattern. Although breed differences for some meat quality parameters were observed, slaughter age had a much more pronounced effect on meat quality parameters. The percentage cooking loss was the lowest (p < 0.05) at 30 months of age. The meat was also darker (p > 0.05) and more red (p < 0.05) at 30 months than at 18 or 24 months of age. The pH24 was higher (p < 0.05) at 24 (5.68 ± 0.05) and 30 months (5.65 ± 0.03) than at 18 months of age (5.48 ± 0.04). A trained sensory panel only detected that Longissimus muscle samples from 18 month old steers were more tender (p < 0.05) than that from 30 month old steers. Similar results were found for Warner-Bratzler shear force values. Marketing steers at 30 months of age resulted in higher production outputs for all the breed types than marketing weaners. For marketing both weaners and 30 month old steers the Nguni herd produced more marketable kilograms live weight than the Simmentaler cross, the Bonsmara cross and the Afrikaner herds. Different marketing systems suitable to the Arid Sweet Bushveld were identified. Each marketing system is discussed in terms of its application, advantages, disadvantages and adaptability to arid regions. It is maintained throughout that a conservative approach to grazing as well as cattle management is critical to ensure stable production systems in arid regions with erratic rainfall patterns. / AFRIKAANSE OPSOMMING: Die oogmerk van hierdie studie is om wetenskaplik gefundeerde riglyne daar te stel wat die begrip van beesvleis produksie vanaf natuurlike weidings in ariede soetveld streke sal verbeter. Beeste van vier ras tipes wat wissel van groot- tot kleinraam tipes (Simmentaler kruis > Bonsmara kruis > Afrikaner > Nguni) is vergelyk in terme van koeiproduksie en effektiwiteit sowel as die groei prestasie, karkas- en vleiskwaliteit van osse op 18-, 24- en 30-maande ouderdom. Osse wat op 18 en 30 maande ouderdom geslag is, is aan die einde van die nat somerseisoen geslag, terwyl osse wat op 24 maande ouderdom geslag is, aan die einde van die droë winterseisoen geslag is. Die Afrikaner kudde (59.8 ± 9.0 %) het ’n laer (p < 0.05) reproduksietempo as die Simmentaler kruis (79.3 ± 12.2 %), Bonsmara kruis (76.5 ± 11.1 %) en die Nguni kuddes (86.1 ± 5.8 %) gehandhaaf. Ras verskille (p < 0.05) ten opsigte van speenmassas en voorspeense groeitempo’s is waargeneem (Simmentaler kruise > Bonsmara kruise > Afrikaners > Ngunis). Die Nguni koei kudde (46.5 ± 5.7 kg/100 kg gedek) was meer (p < 0.05) effektief as die Simmentalerkruis (36.2 ± 5.5 kg/100 kg gedek), Bonsmarakruis (37.7 kg/100 kg gedek) en die Afrikaner kuddes (29.5 ± 5.9 kg/100 kg gedek). Gedurende die droëwinter seisoen het die osse vanaf 7 to 12 maande ouderdom 23.4 ± 1.5 kg in liggaamsmassa toegeneem en vanaf 18 tot 24 maande ouderdom het hulle 20.9 ± 2.0 kg toegeneem. Gedurende die nat somerseisoen het die osse vanaf 12 tot 18 maande ouderdom 109.7 ± 1.8 kg in liggaamsmassa toegeneem en van 24 tot 30 maande ouderdom het hulle 120.3 ± 4.1 kg toegeneem. Die beste (p < 0.05) vetklassifikasie kodes is op 30 maande ouderdom verkry en die swakste (p < 0.05) op 24 maande ouderdom. Simmentalerkruisosse het by alle ouderdomsgroepe die swakste (P < 0.05) vetklassifikasie kodes behaal. Op 30 maande ouderdom het 15 van die 63 osse wat geslag is 3 of 4 permanente snytande gehad, terwyl 47 osse 2 permanente snytande gehad het. Die totale hoeveelheid sowel as die persentasie nier- en omentumvet was die hoogste (p < 0.05) op 30 maande ouderdom en die laagste (p < 0.05) op 24 maande ouderdom. Rugvetdikte het dieselfde patroon gevolg. Alhoewel rasverskille vir sommige vleiskwaliteitsparameters waargeneem is, het slagouderdom’n groter effek hierop. Die persentasie kookverlies was die laagste (p < 0.05) op 30 maande ouderdom. Die vleis was ook donkerder (p < 0.05) en meer rooi (p < 0.05) op 30 maande ouderdom as op 18 en 24 maande ouderdom. Die pH24 was hoër (p < 0.05) op 24 (5.68 ± 0.05) en 30 maande ouderdom (5.65 ± 0.03) as op 18 maande ouderdom (5.48 ± 0.04). Behalwe vir sagtheid, is geen ander ras- of slagouderdomsverskille in die longissimus spiermonsters vir enige van die sensoriese eienskappe wat geëvalueer is, waargeneem nie. ’n Opgeleide sensoriese paneel het slegs waargeneem dat die longissimus spiermonsters van 18 maand oue osse sagter (p < 0.05) was as dié van 30 maand oue osse. Soortgelyke resulte is vir die Warner-Bratzler snyweerstand gevind. Die bemarking van 30 maand oud osse het hoër produksie uitsette vir al die ras tipes opgelewer as die bemarking van speenkalwers. Met die bemarking van beide speenkalf en 30 maand oue osse, het die Ngunikudde meer bemarkbare kilogram lewendige massa as die Simmentalerkruis, die Bonsmarakruis en die Afrikaner kuddes geproduseer. Verskillende bemarkingstelsels wat as geskik vir die Ariede Soet Bosveld beskou word, is geïdentifiseer. Elke bemarking stelsel is in terme van sy toepassing, voor- en nadele asook die toepaslikheid daarvan in ariede streke bespreek. Dit word deurgaans aanbeveel dat ’n konserwatiewe benadering tot beide weidings- en kuddebestuur, krities is om stabiele produksiestelsels in ariede streke met wisselvalige reënvalpatrone te verseker.

No description available.

Department of Animal Science / MSCAGR (Animal Science)

Institute for Rural Development / MRDV

MSCAGR (Animal Science) / Department of Animal Science / The Nguni is a transboundary indigenous Southern African cattle breed. The breed has distinct populations that are adapted to the different ecological zones of Southern Africa. Previous work on characterising the Nguni has been limited to within-country studies. Thus, the aim of the current study was to genetically characterise South African (SA) Nguni, Mozambican Nguni (Landim) and Swazi Nguni populations across Southern African region using a panel of 25 microsatellite markers, recommended by FAO and ISAG for genetic diversity studies. Genotypic data were generated from 90 unrelated autosomal DNA samples of the three cattle populations (SA Nguni n=30, Mozambican Nguni (Landim) n=30 and Swazi Nguni n=30) collected from government research stations and stud herds. Five South African beef cattle breeds’ DNA profiles were obtained from the ARC-DNA database and used as reference populations. A majority of the microsatellite markers were highly polymorphic across the studied populations. High genetic diversity was detected and expected heterozygosity varied from 71% (Landim) to 75% (SA Nguni) with a higher mean number of alleles (MNA) in the SA Nguni (7.52±0.42) compared to the Swazi Nguni (6.92±0.40) and Landim (7.16±0.43) populations. Observed heterozygosity (Ho) (0.597±0.046) compared to expected heterozygosity (He) (0.719±0.022) was lowest for the Swazi Nguni, confirming a relatively high level of inbreeding (FIS=0.158) in that population. An analysis of molecular variance (AMOVA) revealed that 9.61% of the total variation occurred among populations, while 90.39% occurred within populations. Short genetic distance (29.9%) was observed between Landim and Swazi Nguni, with the SA Nguni (>50%) being the most genetically distant population. The distant relationship between SA Nguni and the other two Nguni cattle populations was further confirmed by neighbor-joining (NJ) tree, Principal Coordinates Analyses (PCoA) and Factorial Corresponding Analysis (FCA). The structure of the three Nguni cattle populations clustered independently, despite some evidence of admixture. Additionally, genetic differentiation and population structure within four Mozambican indigenous cattle populations were investigated using the same panel of microsatellite markers. The analysis of unrelated autosomal DNA was performed on 120 animals (Angone n=30, Bovine de Tete n=30, Landim n=30 and Namaacha Nguni n=30), which presented sufficient genetic diversity across all populations. Estimates of mean number of alleles, observed and expected heterozygosities were 6.920±0.20, 0.68±0.02 and 0.71±0.01, respectively. Genetic differentiation among the populations accounted for 8.02% of total genetic variability. Negative (-0.025±0.029) to low positive (0.073±0.050) levels of inbreeding were observed within the four populations. The genetic distance, NJ tree, PCoA and FCA revealed a close relationship between Bovine de Tete and Landim as opposed to Angone and Namaacha Nguni. STRUCTURE analysis assigned the four Mozambican populations independently; however Bovine de Tete and Landim showed relatively higher levels of admixture with each other than Angone and Namaacha Nguni. It can be concluded that SA Nguni, Landim and Swazi Nguni populations accomplish high genetic diversity and they are genetically distant; however, the two latter populations are closely related. These results present useful information / NRF

Ruminant animals consuming low N-diet have been reported to have increased urea reabsorption with the Nguni being categorized as N-recycling ruminant. The enzymes associated with N-cycling are hypothesized to contribute to survival of the Nguni in harsh conditions. Enzymes responsible for such a function needed to be characterized in order to determine their effect in the functioning of the Nguni as opposed to Hereford breed. Crude enzymes from both breeds were separated from most or some contaminants by sephadex G-25, DEAE sephacel, and different affinity column chromatography. CPS and GDH were successfully purified and characterized by LC-MS/MS and further analysed by ProteinPilot™, blasted and matched >95% with those of Bos Taurus. Comparison of characterized enzymes and those which failed to ionise such as ARG, GS and GA was done using kinetics and graphs annotating specific activities. Partial purification and characterization was in part achieved. / Life & Consumer Sciences / M. Sc. (Life Sciences)

Made available in DSpace on 2015-03-26T13:55:24Z (GMT). No. of bitstreams: 1 texto completo.pdf: 371875 bytes, checksum: ebd0743d805bcdc1ccc6a45d01681ac4 (MD5) Previous issue date: 2014-03-12 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / This paper aimed to propose new models to forecast the chemical composition of the non- carcass component; evaluate the equations proposed by BR-Corte (2010) to predict chemical composition of carcass and empty body from bovines using variables of the body and the section between 9th and 11th ribs from data of crossbred animals 3&#8260;4 Zebu x 1&#8260;4 Dutch; and use 3-methilhistidine (3MH) excretion to study the muscle protein synthesis and degradation in both crossbred males and females, at different stages of growth. In chapter 1, the objectives were to develop equations to estimate the non-carcass components chemical composition and to evaluate the prediction equations of chemical composition of carcass and empty body from bovines, proposed by BR-Corte (2010). Data from 130 animals in three experiments (24 castrated males CM; 24 females; and 82 non-castrated males NCM). Over the three experiments, the slaughter procedure was the same, where the gastrointestinal tract was washed to determine the empty body weight and all components of the animal body were weighed individually. The right half carcass was completely dissected and the weight of flash, fat and bones was measured. A sample from both carcass and non-carcass components were collected to determine the chemical composition. The section between the 9th and 11th ribs (HH section) was removed from all castrated males, all females and from 50 non-castrated males and completely dissected to evaluate the chemical composition prediction equations of carcass and empty body from BR-Corte (2010). Equations to estimate composition of the ethereal extract (EE), crude protein (CP), mineral material, calcium, phosphorus, magnesium, sodium and potassium of non-carcass components were proposed. Also, the BR-Corte (2010) equations to crude protein and ethereal extract contents of carcass and empty body were tested and the ones that did not estimate accordingly the known values were readjusted. The equations from BR-Corte (2010) estimated rightly the EE content in carcass from CM, NCM and females; and the EE content in empty body from CM and females. Thus, the forecast equations of CP in carcass from CM, NCM and female; EE in empty body from NCM; and CP in empty body from CM, NCM and females were readjusted. In Chapter 2, the objective was to evaluate the protein synthesis and degradation from castrated males and females, using 3MH. 20 castrated males and 20 females were used. They were with an average age of 12 months and average initial weight of 299 kg for males and 266,7 kg for females. The animals were separated in four groups with eight animals each group (four females and four males) to be slaughtered at 30, 60, 90 and 120 days of confining. The animals were separated in a completely randomized design, in 4 x2 factorial scheme, being two gender condition (castrated males and females) and four confining periods (30, 60, 90 and 120 days). Eight animals (four of each gender) were slaughtered at the beginning of the experiment to determine the initial muscle protein and mass; and four animals of each gender were slaughtered at the end of each period of confining to determine muscle protein and mass. The diet consisted of 45% forage and contained 116.35 g of crude protein / kgDM. To assess protein degradation was performed total collection of urine for three days in all animals slaughtered at the end of each period of confinement for analysis of excretion of 3-methyl-histidine. The urine collection was performed five days before each slaughter. The concentration of 3-methylhistidine in mmol / mmol of creatinine in urine did not differ between males and females (P <0.44) and between periods of confining (P> 0.45). The fractional degradation rate was lower in males than in females (P <0.01) and higher for animals slaughtered at 60, 90 and 120 compared to the slaughter with 30 days of confinement (P <0.01), with no interaction between sex and period of confining (P> 0.38). For the fractional synthesis rate there was no interaction between sex and period of confining (P> 0.31) and sex effect (P> 0.10), but the effect of confinement period (P <0,0,1) was observed, which was lower for animals slaughtered at 30 days compared to the others. The fractional rate of increase showed no interaction between sex and period of confining (P> 0.34), being higher in males (P <0.03) and between different periods of confining (P <0.01), being higher for animals slaughtered at 120 days, followed by 90, 30 and 60 days of confining. It is concluded that the degradation rate is higher in females and the rate of increase is higher in castrated males with no difference between genders for the rate of protein synthesis, which was increased with days on feed. / Objetivou-se com esse trabalho propor novos modelos para predizer a composição química do componente não-carcaça, avaliar com dados de animais cruzados 3&#8260;4 Zebu × 1&#8260;4 Holandês as equações propostas no BR-Corte (2010) para predizer a composição química da carcaça e do corpo vazio de bovinos utilizando variáveis do corpo e seção entre a 9a e 11a costelas e utilizar a excreção de 3-metil-histidina (3MH) para estudar a síntese e degradação proteica muscular em machos e fêmeas cruzados, em diferentes fases de desenvolvimento. No capítulo 1, objetivou-se desenvolver equações para estimar a composição química dos componentes não carcaça e avaliar com dados de animais cruzados 3&#8260;4 Zebu × 1&#8260;4 Holandês, as equações para predição da composição química da carcaça e do corpo vazio propostas pelo BR-Corte (2010) para bovinos. Foram utilizados dados de 130 animais de três experimentos (24 machos castrados (MC), 24 fêmeas e 82 machos não-castrados (MNC)). Nos três experimentos, o procedimento de abate foi o mesmo, onde o trato gastrintestinal foi lavado para determinação do peso de corpo vazio, e todos os componentes do corpo do animal pesados individualmente. A meia carcaça direita foi dissecada completamente, sendo pesadas as quantidades de carne, gordura e ossos. Foram separadas de cada animal uma amostra do componente carcaça e uma amostra do componente não-carcaça para determinação da composição química. Nos machos castrados, fêmeas e 50 dos machos não castrados, foi retirada a seção compreendida entre a 9a e a 11a costelas (seção HH) e realizada sua dissecação completa para avaliação das equações para predição da composição química da carcaça e corpo vazio propostos pelo BR-Corte (2010). Foram propostas equações para estimação da composição de extrato etéreo, proteína bruta, materia mineral, cálcio, fósforo, magnésio, sódio e potássio dos componentes não carcaça; testadas as equações propostas no BR- Corte (2010) para os teores de proteína bruta e extrato etéreo na carcaça e no corpo vazio de bovinos e reajustadas as equações que não estimaram adequadamente os valores observados. As equações propostas pelo BR-Corte (2010) estimaram de forma adequada os teores de EE na carcaça de MC, MNC e fêmeas, e EE no corpo vazio de MC e fêmeas. Assim, foram reajustadas e sugeridas equações para predição da composição da PB da carcaça de MC, MNC e fêmeas, do EE do corpo vazio de MNC e da PB do corpo vazio de MC, MNC e fêmeas. No capítulo 2 objetivou-se avaliar a degradação e a síntese proteica de bovinos machos castrados e fêmeas, utilizando a excreção de 3-metil- histidina. Foram utilizados 40 bovinos cruzados 3&#8260;4 Zebu × 1&#8260;4 Holandês, sendo 20 machos castrados e 20 fêmeas, com idade média de 12 meses e peso inicial médio de 299 kg para os machos e 266,7 kg para as fêmeas. Os animais foram divididos em quatro grupos de oito animais cada um (sendo quatro machos e quatro fêmeas) para serem abatidos aos 30, 60, 90 e 120 dias de confinamento. Oito animais (quatro de cada sexo) foram abatidos ao início do experimento para determinação também da massa e proteína muscular inicial e quatro animais de cada sexo ao final de cada período de confinamento para determinação da massa e proteína muscular. A dieta foi constituída de 45% de volumoso e continha 116,35 g de proteína bruta / kgMS. Para avaliar a degradação proteica foi efetuada coleta total de urina durante três dias em todos os animais abatidos no final de cada período de confinamento para análise da excreção de 3-metil-histidina. A coleta de urina foi realizada cinco dias antes de cada abate. A concentração de 3-metil-histidina em &#956;mol/mmol de creatinina na urina não diferiu entre machos e fêmeas (P>0,44) e entre períodos de confinamento (P>0,45). A taxa fracional de degradação foi menor nos machos que nas fêmeas (P<0,01) e maior para os animais abatidos aos 60, 90 e 120 em comparação aos abatidos com 30 dias de confinamento (P<0,01), não havendo interação entre sexo e período de confinamento (P>0,38). Para a taxa fracional de síntese não houve interação entre sexo e período de confinamento (P>0,31) e efeito de sexo (P>0,10), mas foi observado efeito de período de confinamento (P<0,0,1) que foi menor para os animais abatidos aos 30 dias em comparação aos demais. A taxa fracional de acréscimo não apresentou interação entre sexo e período de confinamento (P>0,34), sendo maior nos machos (P<0,03) e diferente entre os períodos de confinamento (P<0,01), sendo maior para os animais abatidos aos 120 dias, seguidos dos 90 dias e posteriormente dos 30 e 60 dias de confinamento. Conclui-se que a taxa de degradação é maior nas fêmeas e a taxa de acréscimo é maior nos machos castrados não havendo diferença entre os sexos para a taxa de síntese proteica, que foi aumentada com os dias de confinamento.

Ruminant animals consuming low N-diet have been reported to have increased urea reabsorption with the Nguni being categorized as N-recycling ruminant. The enzymes associated with N-cycling are hypothesized to contribute to survival of the Nguni in harsh conditions. Enzymes responsible for such a function needed to be characterized in order to determine their effect in the functioning of the Nguni as opposed to Hereford breed. Crude enzymes from both breeds were separated from most or some contaminants by sephadex G-25, DEAE sephacel, and different affinity column chromatography. CPS and GDH were successfully purified and characterized by LC-MS/MS and further analysed by ProteinPilot™, blasted and matched >95% with those of Bos Taurus. Comparison of characterized enzymes and those which failed to ionise such as ARG, GS and GA was done using kinetics and graphs annotating specific activities. Partial purification and characterization was in part achieved. / Life and Consumer Sciences / M. Sc. (Life Sciences)

MSCAGR (Animal Science) / Department of Animal Science / Milkability, or ease of milking, is the rate at which milk can be completely drawn from a cow’s udder. It is an important functional trait with regard to milking costs as well as udder health. Milkability traits have not been included in the breeding objectives of South African dairy cattle and their genetic parameters in the population have not been estimated. The primary objective of the study was to estimate genetic parameters for milkability traits in South African Holstein cattle. Data consisted of production and milkability records of 1 532 Holstein cows, from 6 herds, participating in the South African National Dairy Animal Recording and Improvement Scheme during the period 2015 to 2016 . Measures of milkability were average milk flow (AMF), maximum milk flow (MMF) and milking time (MT). Genetic parameters were estimated by a multi-trait sire model using the Restricted Maximum Likelihood (REML) procedure. Means for AMF, MMF and MT were 1.99 kg/min, 3.02 kg/min and 5.50 min, respectively. Non-genetic factors affecting variation in milkability traits were herd-year-season of calving, parity and milk yield. Heritability estimates for AMF, MMF, and MT were 0.23±0.09, h2 = 0.41±0.12 and h2 = 0.36±0.11, respectively. Genetic correlations between the three milkability traits were medium to high, ranging from -0.35±0.23 between AMF and MT to 0.79±0.09 between AMF and MMF. Correlations were positive between AMF and MMF and negative between MT and the other two traits. There was an increase in the mean EBV for AMF of 0.002 kg/min (0.0001 kg/min per year) during the period 2002 to 2014. Maximum milk flow also showed an increasing genetic trend of 0.04 kg/min (0.0003 kg/min per year) over the same period. The genetic trend for MT was undesirable, as it increased by 0.0003 kg/min. There is scope for improving milkability through selection, in South African Holstein cattle, as indicated by the moderate to high heritability estimates. The favourable genetic correlations among milkability traits imply that selection on one trait will result in a correlated improvement in the others. Results of the current study provide a basis for including milkability traits in the breeding objective for South African Holstein cattle.