The bioavailability of supplementary lysine and its effect on the energy and nitrogen excretion of adult cockerels fed diets diluted with cellulose.

A basal diet formulated to be deficient in lysine was supplemented with five levels of L-lysine monohydrochloride and each of the resulting diets was diluted with six levels of cellulose. Each of the 30 diets was precision fed (30 g/bird) to adult cockerels which had been fasted for 24 hr, and excreta voided during the 48 hr following feeding were collected. Twelve fasted birds served as controls. Feed and excreta samples were assayed for lysine, energy, and nitrogen. The bioavailability of the natural lysine was 88.2 +/- 2.5% whereas that of the L-lysine HCl was approximately 92%, significantly (P less than .05) less than the 100% often assumed in lysine requirement studies. The supplemental lysine did not significantly affect (P greater than .05) estimates of bioavailable energy [true metabolizable energy (TME), TME corrected to zero nitrogen balance (TMEn)]. Cellulose dilution had no significant (P greater than .05) effect on either lysine or energy availability.