Heritabilities of pre-weaning traits in a multibreed beef cattle herd fitting models with or without a sire genotype x dam genotype interaction

(South African J of Animal Science, 2000, 30, Supplement 1: 118-119

Genetic studies on the South African Mutton Merino: growth traits

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

Genetic parameter estimates for type traits in the South African Jersey breed

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

Genetic parameter estimates for pre-weaning growth traits in Dorper sheep

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

Genetic parameter estimates for the South African Mutton Merino breed

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

Genetic trends for growth in the Gudali and Wakwa cattle breeds of Cameroon

(South African J of Animal Science, 2000, 30, Supplement 1: 36-37

The heritability of acceptability in South African Merino sheep

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

Early growth, survival and litter size in Ethiopian Horro sheep

(South African J of Animal Science: 2000, 30, Supplement 1: 1-3

Factors influencing the price of greasy fleece wool in South Africa

No Abstrac

Phenotypic and genetic relationships between lamb and ewe traits for the Sabi sheep of Zimbabwe

Genetic and phenotypic correlations were estimated between lamb and ewe traits in a flock of Sabi sheep reared at the Matopos Research Station. Direct additive estimates of heritability were: 0.28 ? 0.04; 0.17 ? 0.00; 0.25 ? 0.01; 0.39 ? 0.01; 0.59 ? 0.01; 0.50 ? 0.01; 0.68 ? .03; 0.12 ? 0.003; 0.25 ? 0.01; 0.11 ? 0.00; 0.12 ? 0.00; for birth weight, weaning weight (120 days), 12 month weight, 18 month weight, ewe mating weight, post partum weight, ewe weight at weaning of lamb, total weight of lamb weaned, slaughter weight, hot and cold carcass weights respectively. Genetic correlations between birth weight and other weights to 18 months were high (0.75-0.85), whilst the relationship between weaning, 12 month and 18 month weight was close to unity. The genetic correlation between birth weight and ewe weights (mating, post-partum and dam weight at weaning of lamb) were moderate viz. 0.51 ? 0.08, 0.40 ? 0.09, 0.49 ? 0.07 respectively and were close to unity at 18 months of age viz. 0.96 ? 0.02, 0.92 ? 0.03, and 0.84 ? 0.03 respectively. Total weight of lamb weaned was moderately correlated to birth weight (rg = 0.46 ? 0.15) but tended to be highly correlated with 18 month weight (0.92 ? 0.10) and ewe weights (0.75 ? 0.09-0.91 ? 0.07). The genetic correlation between birth weight and slaughter and carcass weight was moderate and was high at 18 months. The heritability estimates from a univariate logit transformed analysis for fertility, prolificacy and lamb survival were 0.08 ? 0.04, 0.22 ? 0.03, and 0.01 ? 0.02 respectively. The genetic correlation between fertility and lamb weight and ewe weights was low (-0.08 ? 0.004, to 0.06 ? 0.02) and some estimates had large standard errors. The genetic correlation between prolificacy and birth weight was close to zero. The genetic correlations between prolificacy and weaning weight, 12 month weight, 18 month weight, ewe mating, post-partum and ewe weight at weaning were 0.07 ? 0.02; 0.12 ? 0.00; 0.07 ? 0.02; 0.22 ? 0.00; 0.13 ? 0.00; 0.24 ? 0.00 respectively, and that between fertility and prolificacy was negative (-0.17 ? 0.07). Genetic correlations between lamb survival and birth weight, weaning weight, 12 month weight, 18 month weight and total weight of lamb weaned were 0.18 ? 0.00, 0.26 ? 0.00, 0.15 ? 0.00, 0.15 ? 0.00, 0.13 ? 0.00 respectively. Selection for birth weight and total weight of lamb weaned have possible uses in a selection index for the Sabi flock. South African Journal of Animal Science, Vol 31, Issue 3, Oct – Dec (2001) pp.215-222Key WordsFat-tailed hair sheep, Production, Reproductive traits, Lamb survival, Correlation