Genetic parameters, growth rate and reproductive performance of the West African dwarf goat

Production records for a flock of West African Dwarf (WAD) goats belonging to the Livestock Section of the Faculty of Agriculture, Kwame Nkrumah University of Science and Technology (KNUST), Kumasi, were used to analyse the parameters studied. The records covered the period from April, 1970 to November, 1995. The mean age at first kidding was 538.4 days with a minimum of 293 and a maximum of 1204 days. The minimum, maximum and mean kidding intervals were 161, 677 and 280.5 days respectively. Only season of birth significantly (p<0. 05) affected kidding interval. The mean prolificacy of the dose was 200% and it increased with advancing age of dam up to a maximum of 233.3% for six-year-old does. The secondary sex ratio (% males: % females) of 47.55: 52.45 was not significantly (p>0.05) different from the theoretical value of 50: 50. The birth weights of kids were affected significantly (p<0.0l) by type of birth, sex, age of dam, month and year of birth. The mean birth weight was 1.08kg. Birth weight decreased with advancing age of dam in the present study. Single kids had significantly (p<0.0l) higher birth weight (1.26kg) than twin kids (1.12kg), triplet kids (1.00kg) and quadruplets kids (0.83kg). Female kids had a significantly (p<0.0l) lower birth weight (1 .04kg) than male kids (1.13kg). The effect of month and year of birth on birth weight was related to the availability of feed to the pregnant does especially in the last trimester of pregnancy which is largely influenced by rainfall. Weaning weight was affected significantly (p<0.0l) by type of birth, sex, month of birth, year of birth, month of weaning, year of weaning and type of rearing. The overall mean weaning weight was 5.07 kg. Single born kids were significantly (p<0.0l) heavier and grew faster than twin, triplet and quadrupled kids. The weaning weight of male kids 5.20 kg was significantly heavier (p<0.0l) than weaning weight of female kids (4.96 kg). The month of birth and year of birth affected weaning weights significantly (p<0.01).For the month of birth the highest mean weaning weight (5.75 kg) was observed in October and for the year of birth, the highest mean weaning weight was 6.5 kg (1994) and the lowest 3.63 kg (1983). The year of weaning also significantly (p<0.0l) affected weaning weights. The highest mean weaning weight 6.50 kg occurred in 1994 and the lowest 3.88 kg (1984). The overall mean pre-weaning growth rate was found to be 32.85 g/day. The type of birth, type of rearing, month of birth, year of birth, month of weaning and year of weaning significantly (p<0.0l) affected pre-weaning growth rate of kids. The pre-weaning growth rate of male kids (33.46g/ day) was not significantly (p>0.05) different from the pre-weaning growth rate of female kids (32.32g / day). The overall mean post-weaning growth rate (24.39g/day) was significantly (p<0.0l) affected by sex and year of weaning. The heritability estimates and their standard errors obtained by analysis of variance of half-sibs for the combined sexes were Birth weight (0.18 ± 0.001), Weaning weight (0.58 ± 0.002), Pre-weaning growth rate (0.582 ± 0.002) and Post-weaning growth rate (0.21 ±0.004). The repeatability estimates and their standard errors obtained by unbalanced design for the combined sexes were Birth weight (0.07 ± 0.02), Weaning weight (0.43 ± 043) and Pre-weaning growth rate (0.33 ± 0.043). Genetic correlation among birth weight, weaning weight, pre-weaning growth rate and post-weaning growth rates were positive and ranged from 0.245 - 0.980. It was evident from the research that the most useful traits to be selected for improving the mature body weight of the West African Dwarf (WAD) goat are birth weight, weaning weight and post-weaning growth rate up to 12-months.

Source: KNUST