Fat deposition in a broiler sire strain. 3. Heritability of and genetic correlations among body weight, abdominal fat, and feed conversion.

Body weight, abdominal fat, and feed conversion were measured in ad libitum-fed pedigreed chickens of four lines selected from a broiler sire strain. Lines were selected for four generations for a low amount of abdominal fat (AF), a favorable feed conversion (FC), a high body weight after restricted feeding (GR), and a high body weight after ad libitum feeding (GL). A total of 2,400 pedigreed chickens from three hatches were reared by line in groups on litter and 864 chickens were tested for individual feed conversion in individual cages. The h2 from the sire component for the four lines combined were for body weight, .27 (litter) and .22 (cages); for weight of abdominal fat, .54 (litter) and .40 (cages); for percentage abdominal fat, .53 (litter) and .45 (cages); and for feed conversion, .44 (cages). Analysis within line and sex indicated that, in the relatively fat GR and GL lines, sex-linked inheritance could be involved for abdominal fat. In the leaner AF and FC lines this was not the case. Genetic correlations (sire estimate) for the four lines combined were, between body weight and weight of abdominal fat, .58 (litter) and .55 (cages); between body weight and percentage abdominal fat, .36 (litter) and .47 (cages); between body weight and feed conversion, .16 (cages); between weight of abdominal and feed conversion, .43 (cages); and between percentage abdominal fat and feed conversion, .44 (cages). Genetic correlations did not differ significantly between sexes, but in the AF and FC lines, the genetic correlation between body weight and abdominal fat was higher (AF: .80, FC: .76) than in the GR (.14) and GL (.68) lines.