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

The effect of using varied levels of dietary protein with high energy levels in rearing diets on pullet development and on subsequent layer performance in hot climates, was studied using 160 Lohmann White Leghorn pullets. Five replicate groups of 16 pullets, 1 day of age were randomly assigned to each of two series of rearing diets. Pullets in both treatments were fed a 190 g crude protein (CP)/kg starter diet in the ®rst week. Dietary protein level 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 level used during the rearing period in all diets was 12.55 MJ AME/kg. Pullets were reared under a natural cyclic hot temperature ranging as low as 278C measured at 07:00 hours and as high as 348C measured at 13:00 hours. At the beginning of Week 19, pullets were transferred to laying cages and fed two isocaloric layer diets for 20 weeks. Diet 1 used 190 g CP/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 treatment programs was similar, as was feed intake during Weeks 7±14 and 15±18. However, pullets fed diets with 160 g CP/kg had signi®cantly (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 values 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®cantly 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 results of this study showed that when birds were given adequate pullet development, very few differences in egg production parameters resulted due to feeding 160 or Animal Feed Science and Technology