Modified step-up protein feeding regimens for egg-type chickens. 1. Growth and production performance.

Effects of sequential changes in dietary protein on growth from 0 to 20 weeks of age and on egg production from 20 to 72 weeks of age were evaluated with White Leghorn chickens. Four dietary treatments were compared. They consisted of three dietary regimens wherein an 18% crude protein (CP) diet was fed to 1, 2, or 3 weeks of age (Treatments 1, 2, and 3, respectively) and then common 12, 15, and 18% CP diets to 8, 14, and 20 weeks, respectively. These three regimens were compared with a control regimen (Treatment 4) that consisted of feeding 18, 15, and 12% CP diets to 6, 14, and 20 weeks of age, respectively. At 20 weeks of age, 144 birds from each treatment were moved into laying cages for the subsequent 52 weeks of egg production. In comparison with birds on the control feeding regimen, those reared under Treatments 1, 2, and 3 consumed significantly less feed during the 20-week growing period. Birds of Treatments 2 and 3 consumed significantly more protein than those of Treatments 1 and 4. By feeding a 12% CP diet from 1, 2, and 3 to 8 weeks of age, body weights were significantly lower than the average body weight of the control birds, approximately 20, 17, and 13%, respectively, by 6 weeks of age, but only 2 to 4% at 16 weeks of age, and by nonsignificant amounts at 28 weeks of age. Treatment 1 birds consumed 1.8% (significantly) less feed per unit body weight and were 2.6% (significantly) lighter at 20 weeks of age compared with the control birds.(ABSTRACT TRUNCATED AT 250 WORDS)