GENOTYPE, FEEDING REGIMEN, AND DIET INTERACTIONS IN MEAT CHICKENS .1. GROWTH, ORGAN SIZE, AND FEED-UTILIZATION

Allomorphic growth of organs and feed utilization were measured in cockerels from two meat lines known to differ in growth potential under alternate-day and daily feeding of diets differing in nutrient density. The faster growing line consumed more feed and utilized feed more efficiently than the slower growing line. Relative weights of heart and all segments of the gastrointestinal tract except the esophagus were smaller in the faster than in the slower growing line whereas breast, thigh, and drumstick were greater for the faster than the slower growing line. These patterns existed regardless of diet. In contrast, line by feeding regimen interactions were note for most traits; the faster growing line was influenced more by restricted feeding than the slower growing line. Thus, the practice of selecting individuals in a restricted-feeding environment when commercial stocks have feed available to them at all times may be faulty. Although the alternate-day feeding regimen improved feed efficiency, results indicated that full benefit of feed restriction would be realized by feeding a diet higher in nutrient density.