Effect of rearing regimens on pullet growth and subsequent laying performance.

Treatments consisted of eight pullet dietary regimens: high protein with low, medium, or high ME; low protein with high ME, step-up protein, and diets with gradually decreasing protein levels and increasing ME levels with deficient methionine and TSAA levels, recommended methionine levels (TSAA-deficient), or recommended methionine and TSAA levels. Two additional regimens were introduced at 20 wk by selecting light and heavy birds, from caged birds maintained under high protein, medium ME conditions. Laying performance was measured from 20 to 64 wk. During the rearing period, birds fed the low energy and the methionine-deficient regimens consumed less energy (P less than .05). Body weight at 8 wk was affected by initial protein levels (P less than .05), but such effect was not seen after 16 wk of age. Birds on the step-up protein regimen consumed less feed during the laying period but also produced less egg mass (P less than .05). Birds with heavier body weights at 20 wk had better laying performance than birds with lighter body weights (P less than .05). A rearing regimen (0 to 20 wk) that resulted in a total protein intake of 1,140 g and a total ME intake of 20.0 Mcal was shown to control final pullet body weight and maximize laying performance; although at higher ME intake (21.5 Mcal) no detrimental effect was seen.