First available appraisals for 67644 Jersey cows were used to estimate relative magnitudes of additive and selected sources of nonadditive genetic variation, and evaluate corrective mating programs for 13 linear type traits scored linearly from 50 to 99 points. Estimates of additive genetic variances were 11 to 36 percent of within herd-classifier variance, with largest values for stature, strength, rump angle, rump width and udder depth. Dominance components ranged from 2 to 4 times as great as additive components for dairy character, rump width, and the udder traits; fore udder, rear udder height, rear udder width, and suspensory ligament, but were small for the other 7 traits. Maternal effects and the direct additive - additive maternal genetic covariance were unimportant. Sire predicted differences and four measures of dam's merit (dam's phenotypic score, this score relative to herd average, dam's cow index, and half the maternal grandsire predicted difference) were used to predict offspring scores, deviated from herd average. Sire regression coefficients were much larger than those for dam's measures, suggesting that sire evaluations should receive more weight than dam measures in a corrective mating context. Mean squares for effects on offspring scores of interactions between categorical levels of sire predicted differences and dam measures generally were nonsignificant, indicating that additively combining measures is appropriate for predicting offspring performance. Dam's cow index was found to be superior to dam's score for predicting mean performance of offspring groups (e.g., for large groups of offspring or over time) and is therefore preferred for corrective mating decisions. / Master of Science

To evaluate the importance of non-linear relationships between Relative net income per day of productive life (RNI/DPL) and individual traits, 921,915 potential offspring were simulated from all possible matings of 20,487 Jersey cows and 45 active AI sires. Predicted milk yield, fat yield, and 13 linear type traits of potential progeny were used to predict RNI/DPL of all potential progeny. Five methods of mate selection and pairing were evaluated for their effectiveness in choosing mates and the amount of computer time required to choose those pairings. Results of a linear programming (LP) method were used as a comparison for the other four more easily applied methods. Two of the other four methods were not significantly (P > .01) different from the LP method. Although the random pairing method was significantly different, similarity of results, for this method indicated non-linear relationships between RNI/DPL and individual trait scores are of minor importance. A11 four methods used considerable less computer time than the LP method. Analysis of variance for predicted RNI/DPL (all possible offspring) indicated herd, dam within herd, sire, and inbreeding class to be significant (P < .01) variables in determining RNI/DPL. However the sire by dam within herd interaction did not significantly affect RNI/DPL, again indicating non-linear relationships between traits and RNI/DPL were not very important. Regressing PD's, Cl's, and their crossproducts for milk yield, fat yield, and 13 linear type traits showed the relative importance of crossproducts to be minimal in comparison to the linear effects of parental genetic evaluations. / Master of Science

Dairy farming is one of the most important agricultural industries in South Africa, and thus improving the performance of dairy cows, with respect to economically important dairy traits, would be beneficial. Selection of dairy cows has traditionally been phenotypic, but new molecular techniques have made it possible to evaluate phenotypic dairy traits at the DNA level, providing the possibility of more accurate selection. The economically important dairy traits, milk production and reproductive performance, are quantitative traits, and are therefore controlled by many genes and the environment. A number of genes have been identified that have been shown to influence economically important dairy traits, including the lep gene. This gene encodes the hormone leptin, which has been proven to regulate feed intake, energy balance, fertility and immune function. A polymorphism has been identified in the lep gene, which may be associated with economically important dairy traits. This study on a South African Jersey herd investigated the possible association of the polymorphism, RFLP-Kpn 21, with milk production and reproductive performance. The lactation records of fifty Jersey cows that completed their first lactation between 1997 and 2004 were collected, and these cows were genotyped for the RFLP-Kpn 21 polymorphism, located at exon 2 of the lep gene. This involved the extraction of DNA from venous blood, using a salting out technique. The extracted DNA was amplified using PCR primers; the reverse primer included a purposeful mismatch. The role of the purposeful mismatch was to create a recognition site for a restriction enzyme (Kpn 21), thus allowing the alleles of the polymorphism to be identified through a restriction digestion protocol. Two alleles were identified, the C- and the Tallele. The genotype of each cow was identified using PAGE. The significance of the genotype effects on the milk production traits and the reproductive performance traits were estimated using the F-statistic provided by a GLM Univariate analysis. In conclusion, no significant effect of the RFLP-Kpn 21 polymorphism was found for milk yield, butterfat and protein percentage, ICP and SPC (p > 0.05), but a possible association with lactose percentage was suggested by the statistical analysis (p < 0.05). Further investigation of South African Jersey cows will be necessary in order for conclusive results to be obtained. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

The effect of stage of lactation on milk yield, somatic cell counts, mineral and fatty acid profiles in pasture-based Friesian, Jersey and Friesian × Jersey cows was investigated. Twenty Friesian, twenty Jersey and twenty Friesian × Jersey cows were randomly selected from a dairy herd. A total of 202 milk samples were collected and analysed in three stages of lactation. Genotypic differences were observed in milk yield and fat content. Friesian cows produced the highest yield and lowest fat content whereas the opposite was true for Jersey cows (P<0.01). No significant differences were observed in SCC in the different genotypes, but SCC levels were higher in mid and late lactation (P<0.001). There was no effect (P<0.005) of genotype and stage of lactation interaction on Ca, P, Mg, Na, Mn and Bo concentration. Jersey cows had the least concentration of Fe and Cu in all stages of lactation. Strong positive correlations were observed among Ca and P, Mg and Zn. Aluminium had a strong positive relationship with Bo, Fe, Mn and Zn (P<0.001). Generally, SCC had a weak positive relationship with macro elements but a significant negative relationship with microelements. Yield levels were negatively correlated with Mg, Na, Al, Mn and SCC. Pasture ALA, SFA, n-3, n-6/n-3 and PUFA/MUFA concentration did not differ across the study period. Linoleic acid was highest in the second phase which coincides with mid lactation in cows (P<0.001). Highest moisture content coincided with the least fat free dry matter content in early lactation (P<0.001). Significantly high fat content was observed in late lactation than in early lactation. Highest butyric, caproic, linoleic, n-6 and PUFA were observed for Friesian cows. All other fatty acids ratios were not significantly different among different genotypes. Highest CLA, ALA, LA, SFA, PUFA, n-6, and n-3 and atherogenicity index were observed in early lactation whereas desaturase activity indices were highest in late lactation. Strong positive correlations were observed among milk vaccenic, ALA, LA and CLA concentrations. Inverse relationships were observed between SFA and long chain fatty acids. It can be concluded, it may be of advantage to consume milk from early stage of lactation poses a lower risk to coronary diseases and are much safer to consume.

Time budgets, avoidance distance scores-related behaviour and milk yield of pasture-based Jersey, Friesland and crossbred cows. by Madodana Sunson Dodzi The study was conducted at the University of Fort Hare farm to determine the time budgets, the avoidance-related behaviour variables and their relationship with milk yield in three pasturebased dairy genotypes: Jersey, Friesland and crossbreed. Twenty one clinically health dairy cows aged between 52 and 55 months, in mid lactation and comprising of seven cows from each genotype were used in the study. The time spent on different activities (grazing, lying down, standing and others) at pasture was recorded using stop watches across four seasons. The behavioural responses of the three genotypes to humans were determined by recording their avoidance distance scores (AD), exit speed (ES), pen scores (PS), pen behaviour scores (PBS), plat form scores (PLS) and the occurrence of kicking (KCK) and stepping (SPG) during milking on four consecutive days in four seasons. Time spent standing was higher (P < 0.05) for Friesland compared to Jersey and crossbred during the hot-wet season. In the cool-dry season the Jersey spent more time (P < 0.05) grazing than the other breeds. The Friesland and crossbred on the other hand devoted most of their time lying down compared to Jersey in the cool- dry season (P < 0.05). There were season differences in time spent on all activities (P < 0.05). Time spent on grazing was longest in post-rainy seasonal and lowest in hot- wet season (P < 0.05). The longest lying down period was observed in the hot-dry season and lowest in hot-wet season (P < 0.05). iii Daily milk yield Varied (P < 0.05) with genotype with the Friesland and Jersey producing higher yield than the crossbred. The highest amount was produced in hot-dry and the least in hot-wet season. Milk yield was positively correlated (P < 0.05) with lying down. Standing was negatively correlated with milk yield (P < 0.05). The Friesland had the highest avoidance distance scores (P < 0.05) and the Jersey had the lowest avoidance distance scores in all seasons. There was an association (P < 0.05) between genotype and exit speed scores, pen scores and stepping behaviour scores. The Friesland exhibited the highest exit speed scores than the other breeds. The Jersey had the lowest (P < 0.05) kicking behaviour scores. There was a relationship (r = 0.64) between avoidance distance scores and exit speed. Exit speed scores were correlated with pen score(r= 0.23). Milk yield was significant related (r= 0.17) to the occurrence of kicking behaviour. The genotypes showed different levels of sensitivity to season and milk yield was influenced by breed and season. It can be concluded that time budgets vary with season and farmers need to adopt measures that buffer the effect of season on welfare of dairy cows. It can also be concluded that avoidance distance scores differs according to genotype with Jersey being more confident to humans than other two breeds. It is therefore recommended that provision of shades or cooling mechanism should be adopted to buffer the effects of hot-wet season. Improving quality of feed during the cool-dry season may be critical for Jersey cows. Finally positive handling of the dairy cows is recommended in order to improve the welfare and milk yield of pasture based dairy cows.

Eight mature Holstein and Jersey cows beginning their third or later lactation were used throughout this study to evaluate various aspects of the lactation cycle. The lactation (control) diet consisted of 28.8% corn silage, 22.4% alfalfa haylage, and 48.8% concentrate dry matter. Breeds responded differently to the stress of calving. Jerseys had higher plasma somatotropin on day after calving, but Holsteins had higher glucose on day of and day after calving. Plasma parathyroid hormone did not differ between breeds, but Jerseys had higher 1,25-dihydroxyvitamin D₃ than Holsteins on both days after calving. Plasma total calcium and ionized calcium concentrations were lower for Jerseys on both days. Holsteins and Jerseys had similar concentrations of hormones and calcium at 4 and 8 wk. Ionized calcium as a percent of total calcium was elevated at calving, as compared to other times in the lactation cycle, in both breeds. From 9 to 21 wk, 4 of 8 Holsteins and 4 of 8 Jerseys were fed a diet supplemented with tallow. Holsteins fed tallow had lower somatotropin than Holsteins fed control diet at 14 and 18 wk. Plasma glucose, parathyroid hormone, and 1,25-dihydroxyvitamin D₃ were similar between tallow- and control-fed cows in both breeds. Plasma total calcium and ionized calcium were higher at 20 wk for Holsteins and Jerseys fed tallow. Dry matter intake was not influenced by diet in either breed. However, Holsteins, but not Jerseys, fed tallow produced more milk and higher body weights than Holsteins fed the control diet. Balance trials results indicated dietary tallow addition increased energy intake, energy digestibility, and metabolizable energy, but it decreased partial efficiency of metabolizable energy utilization for lactation. Although digestibility of calcium and magnesium was unchanged, tallow-fed cows were in greater positive calcium and magnesium balance than control-fed cows. Stage of lactation had little effect on specific gravity, shear stress, percent mineral, and histological measurements of biopsied rib samples. However, Jersey rib had higher specific gravity than Holstein rib. All cows had similar bone histological features throughout lactation. / Ph. D.

Stearoyl-CoA desaturase1 (SCD1) catalyzes the synthesis of conjugated linoleic acid (CLA) and mono-unsaturated fatty acids (MUFA) in the mammary gland of ruminant animals. We hypothesized that single nucleotide polymorphisms (SNPs) in the coding region, 5' and 3' untranslted regions (UTRs) of the SCD1 gene would influence the activity of SCD1 enzyme and consequently account for some within-breed variations in milk CLA and MUFA. Sequence analysis of the coding region of the SCD1 gene of Jerseys and Holsteins revealed c.702A&rarr;G, c.762T&rarr;C and c.878C&rarr;T SNPs in exon 5 in both breeds and c.435G&rarr;A in exon 3 in Holsteins. The SNPs resulted in: A (G435A702T 762C878), A1 (A435A702T 762C878), B (G435G702C 762T878) and B1 (A435G702C 762T878) coding variants in Holsteins and only variants A and B in Jerseys. Only SNP 878C&rarr;T resulted in a non-synonymous codon change resulting in p.293Ala and p.293Val protein variants or alleles at the SCD1 locus. Subsequent association studies found significantly higher C10 index, C12 index and C14 index and consequently higher concentrations of C10:1 and C12:1 in p.293AA cows compared to the p.293VV cows in both breeds. The SCD1 genotype had no influence on concentrations of C141, C16:1, C18:1 and CLA in both breeds. / Sequence analysis of the 5' and 3' UTRs revealed no SNPs in the 5'UTR and a total of 14 SNPs in the 3'UTR of both breeds. The SNPs were in complete linkage disequilibrium resulting in 3 haplotypes or regulatory variants: H1 (G1571G1644C1763C2053A2584 A3007C3107G3208 T3290G 3497G3682A4399C4533G4881), H2 (G1571G1644A1763C2053A 2584G3007 C3107G3208T3290G3497G 3682A4399C4533G4881) and H3 (T 1571C1644A1763 T2053G2584G3007T 3107A3208C3290A3497A3682T 4399T4533A4881) in Holsteins and only H1 and H3 variants in Jerseys. A subsequent association study involving 862 Holstein cows, found the H1 regulatory variant to be associated with higher C10 and C12 desaturase indices and consequently with higher concentrations of C10:1 and C12:1 compared with the H3 variant. The effects of the H2 variant were intermediate to those of H1 and H3. 3'UTR genotype had no influence on the concentrations of C14:1, C16:1, C18:1 and CLA. The concentrations of C10:1 and C12:1 in milk fat could therefore be due to effects of SNPs in the open reading frame and the 3'UTR regions of the SCD1 gene. These results indicate that SNPs in the coding and 3'UTR regions of the SCD1 gene could be used as markers for genetic selection for increased C10:1 and C12:1 contents of milk.

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