Influence of genetic differences in feed efficiency on carcass composition of young chickens.

The carcass composition of young chickens differing in efficiency of feed utilization was obtained to study changes in the carcass composition associated with differences in efficiency of feed utilization. As the efficiency of conversion of food to tissue was changed, there were associated changes in carcass moisture and lipid, regardless of differences between different populations in variability for growth rate. Carcass moisture was increased and carcass lipid was decreased in chickens with relatively better conversion of food into carcass. Carcass protein was significantly increased in chickens with better efficiency of feed utilization in one population, but not in another. Changes in carcass composition associated with efficiency of feed utilization were similar regardless of whether differences in efficiency were due to gain or to a combination of gain and consumption. Significant sex differences in carcass moisture, lipid, and protein were observed in the faster-growing broiler population but not in the lines selected from a slower-growing randombred population. There was a significant decrease in 16:1 and an increase in 18:0 fatty acids of chickens with a lower feed conversion ratio.