Modified Step-Up Protein Feeding Regimens for Egg-Type Chickens. 2. Protein Level Influence on Growth and Production Performance

Abstract

Abstract The influence of dietary protein changes on growth from 0 to 20 weeks of age and on egg production from 20 to 72 weeks of age was studied with a commercial strain of White Leghorn chickens. Eight dietary treatments were compared to evaluate two aspects of step-up protein regimens for egg-type pullets: 1) the crude protein (CP) level fed the initial week, and 2) the duration of feeding the 12% CP diet. Treatment 1 served as the control regimen and consisted of feeding 18, 15, and 12% CP diets to 6, 14, and 20 weeks of age, respectively. The percent CP with the respective weeks fed (in parentheses) for Treatments 2 through 8 were as follows: Treatment 2, 18% (0 to 1), 12% (1 to 8), 15% (8 to 14), and 18% (14 to 20); Treatment 3, 18% (0 to 1), 12% (1 to 10), 15% (10 to 16), and 18% (16 to 20); Treatment 4, 18% (0 to 1), 12% (1 to 12), 15% (12 to 16), and 18% (16 to 20); Treatment 5, 16% (0 to 1), 12% (1 t o 10), 15% (10 to 16), and 18% (16 to 20); Treatment 6, 16% (0 to 1), 12% (1 to 12), 15% (12 to 16), and 18% (16 to 20); Treatment 7, 20% (0 to 1), 12% (1 to 10), 15% (10 to 16), and 18% (16 to 20); and Treatment 8, 20% (0 to 1), 12% (1 to 12), 15% (12 to 16), and 18% (16 to 20). All diets were fed ad libitum. At 20 weeks of age, 72 birds from each treatment were housed in laying cages for 52 weeks of egg production. Cumulative feed intake through 20 weeks of age for birds reared on Treatments 2 through 8 was generally less than that of the control birds. Birds reared on Treatments 4 and 8 consumed significantly less protein than the control birds. By 20 weeks of age, average body weights for Treatments 2 through 8 were 4.0, 6.0, 7.6, 4.3, 2.7, 4.6, and 7.6% lighter, respectively, and significantly different from that of the control birds. Dietary treatment did not influence mortality during the growing period. By 28 weeks of age, there were no significant body weight differences among any of the treatments. Age at 50% production, hen-day production, livability, egg weight, percentage egg size, shell deformation, Haugh score, feed per hen-day, and feed per dozen eggs also did not differ significantly among any treatments. Results of this study indicate that feeding a 16 to 20% CP diet for the 1st week of life, followed by a 12% CP diet through 8 to 12 weeks of age, 15% CP to 16 weeks, and 18% CP to 20 weeks of age, produced smaller birds at 20 weeks of age with less total feed intake than the control birds. None of the egg production parameters studied were significantly affected.