Production parameters for Boer goats in South Africa

[摘要] English: In the first study performance data from 465 Boer goat rams tested in a central performance test in the Northern Cape Veld-Ram Club from 1989 to 2007 were analysed to determine the relationship between performance and sale price. Rams were subjected to extensive management conditions on natural pastures for 160 days and finished-off in a feedlot for 50 days. Upon the conclusion of the entire test period, the rams were auctioned. Performance information was available for buyers for decision making. Traits analysed included final weight (FW), final weight index (FWI), average daily gain (ADG), average daily gain index (ADGI), growth per day of age index (ADOI), Kleiber ratio (KR), auction weight (AW), scrotal circumference (SC), selection index (SI) and sale price (SP). Stepwise regression analyses, using proc GLM of SAS were performed to identify variables that significantly influenced sale prices. Final weight was significant in eight out of eighteen years, auction weight was significant in six of the seven years measured and selection index influenced prices in seven out of ten years. Scrotal circumference, average daily gain, final weight index, average daily gain index and Kleiber ratio had little influence on sale price. Growth per day of age index did not show any influence on sale price. Price was positively correlated (P<0.05) with many of the performance traits. All significant correlations were moderate to high and ranged from 0.37 to 0.80. The amount of variation in sale price accounted for by the performance traits ranged from 15% in year 1991 to 65% in 1998. The most important traits influencing sale price (SP) were final weight, auction weight, and selection index. The results indicated that buyers of stud rams put more emphasis on production traits such as body weight and that they recognize the importance of performance data as shown by their preference for animals with high selection indices. In the second study data consisting of 3855 records and collected from 1998 to 2008 were analysed to estimate genetic parameters for economic traits in two Boer goat flocks. The traits investigated were weaning weight and post-weaning weight. Least square analysis was used for estimation of environmental effects. Genetic parameters were estimated from single and bivariate trait analyses using ASREML software fitting animal models. By ignoring or including maternal additive genetic effects and their covariance and maternal permanent environmental effects seven different models were fitted for each trait. The fixed effects of sex, type of birth, age of dam, year of birth, herd, season and age of lamb, were all significant (P<0.05) for both traits. The direct heritability estimates varied from 0.24 for weaning weight to 0.31 for post-weaning weight. The corresponding maternal permanent environment due to the dam was 0.10 and 0.44 respectively. The maternal heritability (0.03) for weaning weight was lower than its corresponding direct heritability. Estimates of genetic parameters in this study confirmed that selection for weaning weight would result in genetic improvement of Boer goats.

[发布机构] University of the Free State