Divergent selection of lean and fat lines of broilers over eight generations using plasma very low density lipoprotein as selection criterion

Abstract

1. Male and female broilers from a male grandparent line have been selected over 8 generations on the basis of low or high plasma very low density lipoprotein (VLDL) concentration. This has given lines of lean and fat broilers.

2. Plasma VLDL concentration in the two lines has diverged steadily and showed a 7‐fold difference in the 8th generation.

3. Divergence of other traits, including abdominal and total body fat, body protein and conversion efficiencies of food and dietary protein has continued but body weight has not changed with selection.

4. Divergence of body composition and nutrient conversion relative to a commercially selected control line derived from the same origin as the experimental lines has been slightly greater for the fat line.

5. In the lean line, females have been more responsive to selection with the result that body compositions of lean line males and females at 7 weeks have become quite similar.

6. Plasma VLDL concentration decreased little in the lean line over the later generations and showed a lower phenotypic correlation with abdominal fatness than in the fat line in the 8th generation. A limit to selection for body fatness using this criterion may be approaching in the lean, but not in the fat, line.