The influence of proportion of Hereford breeding in a multibreed synthetic beef cattle population on birth weight and weaning weight

(South African J of Animal Science, 2000, 30, Supplement 1: 124-126

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

The influence of outliers on a model for the estimation of crossbreeding parameters for weaning weight in a beef cattle herd

Data on 17348 weaning weight records from a beef cattle crossbreeding operation were used to determine the effect of outliers on regression coefficients. Different criteria were used for detecting potential influential points. Eliminating a small number (932 or 5.4%) influential points resulted in the improvement of the model fitted. The R2 values increased from 41% to 49% while the mean square error was reduced from 672.9 to 500.4. The use of diagnostic statistics for detecting influential observations is recommended before any analysis is performed. South African Journal of Animal Science Vol.32(3) 2002: 164-17

Pre-weaning growth traits of the Hereford breed in a multibreed composite beef cattle population

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 and environmental parameters for ewe productivity in Merinos

Data of 3272 lambing records collected on 818 ewes born from 689 dams and sired by 371 rams were used in the evaluation of ewe lifetime productivity (total number born, number weaned and total weight weaned). These records were collected from ewes born from 1969 to 1994 and which gave birth during the period from 1971 to 1999. Year of birth of ewe and ewe two-tooth liveweight affected the ewe productive traits investigated. Multiple born ewes were superior both in total number of lambs born and weaned compared to singles. Heritability estimates of 0.23, 0.17 and 0.20 were obtained for total number of lambs born (TLB), total number of lambs weaned (TLW) and total weight of lamb weaned per ewe over four lambing opportunities (TWW), respectively. For total weight weaned per ewe over the first lambing opportunity (TWW1) a heritability of 0.02 was estimated. Genetic correlation estimates of -0.10, 0.57 and 1.00 were obtained between TWW1 and TLB, TWW1 and TLW and TWW1 and TWW, respectively. High and positive genetic correlations ranging from 0.61 to 0.92 were estimated between ewe lifetime traits. Genetic progress could be expected when selection is applied on these traits. South African Journal of Animal Science Vol.32(3) 2002: 154-16

Estimates of crossbreeding parameters in a multibreed beef cattle crossbreeding project

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 0.05) for WW. Individual heterotic effects for BW were significant (P 0.05) for both BW and WW. (South African Journal of Animal Science, 2000, 30(3): 193-203

Genetic parameters of testicular measurements in Merino rams and the influence of scrotal circumference on total flock fertility

Genetic parameter estimates for scrotal circumference (SC), testis diameter (TD) and two-tooth liveweight (LW) were obtained for 1380 two-tooth Merino rams born from 1986 to 1998 on the Tygerhoek Experimental Farm. The effect of SC of service sires (n = 263) on ewe fertility was also investigated. Year of birth, selection group and LW were significant sources of variation for both SC and TD. SC had a significant effect on ewe fertility. Heritability estimates ranged from 0.29 to 0.40, 0.25 to 0.38 and from 0.49 to 0.52 for SC, TD and LW, respectively. Adjustment for LW decreased heritability estimates of SC and TD and the genetic correlations between the latter traits. Rams with an unadjusted SC of less than 30 cm should not be used. South African Journal of Animal Science Vol.32(2) 2002: 76-8

Heritabilities of reproductive traits in a beef cattle herd using multitrait analysis

(South African J of Animal Science, 2000, 30, Supplement 1: 140-141

Genetic and phenotypic variation of some reproductive traits in Egyptian buffalo

The objectives of this study were to determine the effects of season, year of calving and parity on lactation period, calving interval, number of days open and dry period in Egyptian buffalo, and to estimate genetic and phenotypic parameters for these traits using a multi-trait animal model. Season of calving, year of calving and parity affected the traits studied. Heritability estimates for lactation period, calving interval, dry period and number of days open were 0.09, 0.07, 0.13 and 0.08 respectively and repeatability estimates were 0.27, 0.14, 0.27 and 0.19 respectively. Estimates of the permanent environmental component (c2) were low. Genetic correlations between these traits were low and positive, except for that between lactation period and dry period, which was negative. A similar pattern was observed for phenotypic correlations, but these were higher than those observed for genetic correlations. South African Journal of Animal Science, Vol 31, Issue 3, Oct – Dec (2001) pp.195-199 Key Words Buffalo, Calving interval, Days open, Dry period, Heritabilit

Heritability estimates derived from threshold analyses for reproduction and stayability traits in a beef cattle herd

The object of this study was to estimate heritabilities and sire breeding values for stayability and reproductive traits in a composite multibreed beef cattle herd using a threshold model. A GFCAT set of programmes was used to analyse reproductive data. Heritabilities and product-moment correlations between predicted breeding values for stayability at 36, 48, 60, 72 and 84 months of age, calving success and longevity were estimated. The estimated heritabilities on the underlying scale for these traits were 0.06, 0.10, 0.06, 0.03, 0.11, 0.03 and 0.08 respectively. Product-moment correlations between breeding values for stayability traits were low. The highest correlation of 0.22 was obtained between the ages of 36 and 48 months. Heritability estimates and correlations between traits appear to be of such a low magnitude that selection for these characteristics would result in limited genetic improvement, and also indicate that sires had little influence on the stayability, longevity or calving success of their daughters. (South African Journal of Animal Science, 2001, 31(1): 25-32