Egg production of light and medium hybrids given diets varying in energy level during the chick, rearing and laying stages

Abstract

Synopsis A total of 1000 birds, one‐half of which were light and the other half medium hybrids, were given diets containing either high or low levels of metabolisable energy ad libitum during the chick (0.6 weeks), rearing (6–16 weeks), early laying (first 8 months) and late laying (last 4 months) stages. The medium hybrids ate more and were heavier than the lighter hybrids at all stages. More eggs were laid by the light than by the medium hybrids but the latter laid larger eggs so that the total weight of eggs laid did not differ significantly between the two groups. Medium hybrids given a low‐energy chick diet laid more eggs subsequently than those given a high‐energy chick diet, while the opposite result was obtained for the light hybrids. Birds given a low‐energy rearing diet were lighter at 16 weeks and subsequently laid more eggs than birds reared on a high‐energy diet. During the first part of the laying period consumption of the low‐energy diet was greater than that of the high‐energy diet, but the level and efficiency of egg production were the same for both dietary treatments. Mortality during lay was not significantly affected by dietary treatment or breed.