Requirement of the laying hen for apparent fecal digestible lysine

A study was conducted to determine the requirement for lysine of a White Leghorn strain of hens with a body weight of approximately 1,600 g. Before starting the experiment, apparent fecal digestibility of amino acids of the basal diet was determined in an in vivo digestibility trial with six individually housed hens. The basal diet used was based on corn and soybean meal and contained 0.65% total and 0.49% apparent fecal digestible lysine. To the basal diet, seven graded dose levels (0.04, 0.08, 0.12, 0.16, 0.20, 0.24, and 0.28%) of lysine as L-Lysine-HCl were added. The experimental diets were fed for 12 wk, covering the early stage of laying from 24 to 36 wk of age. Each experimental diet was fed to 60 individually caged housed birds. The dietary lysine requirement was found to be higher for maximizing efficiency of feed utilization than for obtaining maximum egg mass yield. Based on the feed conversion efficiency and at an egg mass yield of 57 g/hen-d, the requirement for total lysine was estimated to be about 900 mg/hen-d. From the results of the digestibility trial, it was calculated that the estimated requirement for total lysine was equivalent to 720 mg apparent fecal digestible lysine per hen-day