Efficiency of protein utilization in male and female broiler chickens

The efficiency of dietary protein utilisation in broiler chickens was studied by conventional balance techniques and by digestion and metabolism of ¹⁵N-labelled protein in the diet. Between 16 and 30 days of age, male chickens tended to be heavier and to ingest more feed than female chickens: however, female chickens tended to absorb and utilize dietary protein more efficiently than male chickens. Whole-body synthesis rate did not differ between sexes and was 6.7-7.5 times the protein absorption rate. Only about 10% of the protein synthesized was deposited in tissue gain whereas 90% was degraded. Fractional protein synthesis rates were determined from the decline in enrichment in small intestinal, liver and breast muscle samples taken sequentially from birds that had earlier ingested ¹⁵N-labelled feed. FSRs declined with age but did not differ between sexes and were 44-52, 23-29 and 15-18 %/d, respectively.