Growth and carcass characteristics of chickens from lines divergently selected for growth or fatness
Ricard, F.H.; Leclercq, B.
Genetique Selection Evolution 17(4): 549-560
Chickens from 4 experimental lines were raised in the same environment to 9 weeks of age. These lines were selected either for high or low growth rate (X-33 and X-44) or for high or low abdominal fat content (fat and lean lines). All the birds were weighed at 3, 6 and 9 weeks, breast angle was measured on living chickens at 9 weeks. Then, 32 cockerels per line were slaughtered, carcass breast angle was obtained, french dressed (effile) carcasses and abdominal fat deposits were weighed. Because of the very different genotypes, differences between lines were observed for all the measured characteristics. Between 3 and 9 weeks of age, weight gain of the lean birds was slightly but significantly higher than the gain of the fat birds. Average phenotypic correlations with live body weight were .994, .59, .40, .29, and .26 for effile carcass weight, abdominal fat weight, abdominal fat percentage, effile carcass weight/live weight ratio and carcass breast angle, respectively. Changes in effile carcass weight variations strictly followed those of live body weight and the 4 regresssion lines (effile weight on live weight) maybe combined. Fatness variations showed specific patterns between lines. Correlation coefficients with breast angle were practically zero for fat and lean lines, and 0.45 for X-33 and X-44 lines. Allometric coefficients of abdominal fat weight on live weight varied from 1.9 (fat line) to 3.5 (lean line) and the 4 regression lines obtained withraw values are statistically different. However, a common regression line could be drawn for the X-33 and X-44 lines. Our results corroborate the hypothesis of an effect of the chicken genotype on relationships between carcass characteristics.