Response of Laying Hens to Different Dietary Lysine Intakes

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Abstract
Two sequential experiments, each lasting 420 days, were conducted to test whether different strains of laying hen differ in their response to various lysine intakes. In Expt. 1 five diets, calculated to be isocaloric (11.3 MJ ME/kg) and varying in lysine content from 460 to 870 mg/kg were fed to each of 5 strains, 3 commercial White Leghorn (WL) hybrids (Hisex, LSL and Shaver) and 2 experimental cross bred strains. In Expt. 2 five isocaloric (11.4 MJ ME/kg) diets with calculated lysine contents ranging from 480 to 880 mg/kg were fed to each of 4 strains, 2 commercial WL hybrids (LSL and Shaver), one commercial Rhode Island Red hybrid (Hisex Brown) and 1 experimental strain. To test whether lysine was the first limiting amino acid in the diets used, 0.1% L-lysine HCl was added to 4 of the original diets used in Expt. 1 and fed to the WL strains. Large variation in egg output between strains of birds was observed. Second degree polynomial equations were fitted to the data obtained from each experiment for each strain separately and common functions for the WL strains in each experiment were also calculated. Response curves based on these equations are illustrated. Under the conditions of the present experiments the daily lysine requirements for maximum egg output were estimated to be in the range 820 to 1023 mg/hen. Economically optimum intakes of lysine for the different strains used varied from 766 to 956 mg/hen daily. Increased feed intake was associated with feeding diets marginally inadequate in protein, whilst markedly deficient diets caused a decrease in feed intake in the early weeks, followed by an adaptation observed at least in Expt. 1. Poor plumage condition, excessively long claws and high incidence of foot damage were found to be associated with feeding low protein diets.