Effects of dietary protein and strain on the growth of broiler breeder pullets from zero to five weeks of age.

In a series of four experiments, the effects of differences in dietary protein intake on BW, skeletal growth and the weight of the Pectoralis major muscle was studied in Hubbard Standard and Hubbard Hi-Y broiler breeder pullets. In Experiment 1, pullets were fed diets with either 15, 17, or 19% CP from 1 to 21 d. There was a linear increase in BW gain and feed consumption with each increase in CP and Hubbard Standard pullets consumed significantly more feed than Hubbard Hi-Y pullets. From 21 to 34 d, pullets were subjected to feed restriction every day (ED) or every-other-day (EOD). On Day 35, pullets were given ad libitum access to feed and ED-restricted pullets consumed significantly more feed than EOD-restricted pullets through 3.5 h postfeeding. In Experiment (Exp.) 2, pullets were fed the 19% CP diet for approximately 14 d (300 g) or 20 d (600 g) before being switched to the 15% CP diet. In Experiment 3, the 19% CP diet was fed for exactly 7 or 21 d before switching to the 15% CP diet. In all experiments, Hubbard Standard pullets weighed significantly more than Hubbard Hi-Y pullets and had increased overall skeletal growth. When the pullets from both strains were restricted to only 380 g BW at 28 d, (Exp. 3) the longer period of protein intake significantly enhanced breast muscle weight but there were no significant strain differences. When BW at 28 d was increased to 480 g, (Exp. 2), dietary protein and strain differences were observed.