Growth response of immature brown-egg strain pullets to varying nutrient density and lysine

Three trials were conducted to quantify growth of brown-egg strain pullets up to 126 days of age when fed diets of varying energy, protein, or lysine concentration. Birds were grown in 60 X 50 cm cages with 12 birds per cage (0 to 42 days) or six birds per cage (42 to 126 days). Trial 1, using eight replicates per treatment, involved conventional pullet diets or diets formulated to meet methionine and lysine needs only, with no constraint on crude protein formulated at two energy levels. Both white-egg and brown-egg strains were smaller (P 0.01) when fed diets formulated to only methionine and lysine requirements. When high-energy diets were used, white-egg but not brown-egg pullets exhibited comparable growth depression (P 0.01) in response to amino acid intake. In Trial 2, brown-egg pullets were fed diets varying in energy (2,500 or 3,000 kcal ME/kg) and crude protein (15 to 21.5%). Four dietary treatments were each tested with seven replicate groups of 12 caged pullets. Results confirm the apparent refractory feed intake response of the brown-egg bird to varying diet energy density. Only during the 84- to 126-day grower period did birds behave in the classical manner of eating less feed (P 0.01) when offered higher-energy diets. Trial 3 involved growth response to graded levels of dietary lysine. Pullets fed 0.68 to 0.98% lysine showed maximal weight gain to 42 days, whereas after 84 days, diet lysine from 0.38 to 0.86% had no effect on growth. It was concluded that the brown-egg pullet is less refractory than the Leghorn pullet in terms of adjusting feed intake to dietary energy concentration