The use of step-down and modified constant protein feeding systems in developing pullets reared in hot climates

The effect of using varied levels of dietary protein with high energy level s in rearing diets on puller development and on subsequent layer performanc e in hot climates, was studied using 160 Lohmann White Leghorn pullets. Fiv e replicate groups of 16 pullets, 1 day of age were randomly assigned to ea ch of two series of rearing diets. Pullets in both treatments were fed a 19 0 g crude protein (CP)/kg starter diet in the first week. Dietary protein l evel series used during Weeks 2-6, 7-14, and 15-18 were 190, 160, and 135 g CP/kg, respectively, for the decreasing protein series treatments and 160, 160, and 135 g CP/kg, respectively, for the semi-constant series. Energy l evel used during the rearing period in all diets was 12.55 MJ AME/kg. Pulle ts were reared under a natural cyclic hot temperature ranging as low as 27 degrees C measured at 07:00 hours and as high as 34 degrees C measured at 1 3:00 hours. At the beginning of Week 19, pullers were transferred to laying cages and fed two isocaloric layer diets for 20 weeks. Diet 1 used 190 g C P/kg and 4 g methionine/kg and Diet 2 used 160 g CP/kg and 3.4 g methionine /kg. Each diet was fed to half of the pullets within each rearing treatment program. During the rearing period, body weight of pullets in both treatme nt programs was similar, as was feed intake during Weeks 7-14 and 15-18. Ho wever, pullets fed diets with 160 g CP/kg had significantly (p<0.05) higher feed intake than those fed the 190 g CP/kg diet during Weeks 2-6. Hen-day egg production, days to 50% egg production, egg weight and Haugh unit value s were not affected by dietary protein treatments during the rearing period . Reducing protein levels from 190 to 160 g CP/kg in laying hen diets signi ficantly increased egg production during Weeks 27-30 and 35-38, but reduced egg weight during Weeks 23-30 period of egg production. In addition, the r esults of this study showed that when birds were given adequate pullet deve lopment, very few differences in egg production parameters resulted due to feeding 160 or 190 g CP/kg during the early production period under this cl imatic condition. (C) 2000 Elsevier Science B.V. All rights reserved.