Some effects of changing protein levels during the pullet laying year

Abstract

Three diets containing 12, 14 and 16 per cent crude protein were fed to laying pullets from 23 to 63 weeks of age. The laying year was divided into three periods of 10, 15 and 15 weeks to examine the effect of feeding these diets at different stages of lay. Eighteen treatments were used, representing all possible combinations of three diets in the first period, three diets in the second period and two diets (16 and 12 per cent) in the third period. Two groups of 75 pullets were allocated to each treatment. In each period the diet had a significant effect on the rate of lay, egg output (g./day) showed a linear regression on protein intake. There was no indication that the amount of protein needed to maximise egg output was any less in one period than another, although the level of maximum output varied substantially as the year progressed. Where the feeding of an inadequate level of protein in one period was followed by a higher level in the next, liveweight showed a marked recovery but there was little evidence of compensatory egg production. When the protein of the diet was reduced from 16 to 12 per cent, rate of lay fell sharply to a level below that of birds which had received the 12 per cent protein diet throughout.