The developmental characteristics of two strains of chickens selected for differences in mature abdominal fat pad size.

Genetic selection for mature abdominal fat pad size has resulted in establishing lean and obese lines of chickens. Although the selection was made with mature hens, studies with the progeny showed that obesity could develop as early as 6 weeks of age. Body weights in the two lines diverged by 7 weeks of age although significant differences in feed intake were not seen until the fourteenth week. A pair-feeding study was conducted from 7 through 17 weeks of age. The results showed that pair-feeding greatly reduced the lipid deposited in the obese line. The two strains differed substantially in carcass lipid content, but the proportion of total body lipid contributed by the carcass, viscera, and abdominal fat pad was similar in both lines.