Genetic variation of abdominal fat, body weight, and carcass weight in a female broiler line.

Pedigreed matings in a commercial purebred female broiler selection line produced 311 males and 341 females, which were slaughtered at 50 days of age. Coefficients of variation of abdominal fat weights were higher than live and carcass weights. The coefficient of variation was reduced when abdominal fat was regressed on live weight or when percentage of live or carcass weight was used. Leaf fat was approximately two-thirds and gizzard fat was approximately one-third of the total abdominal fat. Heritabilities for abdominal fat were high, and the genetic correlations between the fat and live or carcass weights ranged from .43 to .50 in males and .32 to .40 in females. The phenotypic correlations between fat and live weight were reduced when abdominal fat weight was subtracted from live weight, showing that the part-whole relationship between abdominal fat included in live body weight increased the correlations. The heritabilities indicate that it should be possible to reduce abdominal fat by selection, and the genetic correlations signify that a method has to be devised to increase body weight while simultaneously reducing abdominal fat weight.