Efficiency of feed utilization and rate of feed passage through the digestive system.

The relationship of efficiency of feed utilization determined by the feed conversion ratio (FCR) to the rate of feed passage through the digestive system of juvenile chickens was studied and three different methods of measuring feed passage rate (FPR) were evaluated. The FPR did not differ between sexes that had different FCR, nor did it differ between commercial broiler strains that differed in FCR. Feed restriction did not affect FPR. There was little correlation between FCR and FPR in any of the groups evaluated and the FPR was similar for high- and low-FCR groups. There was some evidence for increased FPR in birds grown at 32.2 C compared with those grown at 26.7 C. Similar results were obtained for FPR whether the tracer dye was given in the feed, or in a gelatin capsule, or no tracer dye was used. Repeatability of FPR obtained on the same individuals at different ages was very low.