The Response to One Cycle of Divergent Selection for Abdominal Fat in Broilers Raised Under Different Conditions

Abstract

One cycle of divergent sib selection, for or against abdominal fat weight, combined with within-family selection for body weight, was performed in a population of a commercial female grandparent line (White Rock type). Chicks from the first generation (S1 G1) of high-fat (HF) and low-fat (LF) selection lines were raised in three different environmental and climatic conditions. A second generation (S1 G2) of the selection lines was obtained by within-line selection for body weight only.The HF line had about 60% more abdominal fat than the LF line in all three environments. The realized heritability of this trait was calculated to be .73, almost identical to the heritability estimated from the base population. The LF line mean body weight was between 1% and 5% lower than that of the HF line. This difference was not significant and it was almost abolished in S1 G2, after both lines were selected for body weight only. The difference between lines in abdominal fat weight was increased to 80% in S1 G2. It can be concluded that reduction in abdominal fat weight was not associated with a decrease in body weight. Selection for body weight, in a line previously selected against abdominal fat, did not reverse the reduction in fat. The difference between the HF and LF lines had the same magnitude in both sexes and under different environmental conditions that increase or decrease fat deposition.