Lysine supplementation of low-protein diets for broiler breeder males

Two experiments were conducted to assess the impact of supplemental L-lysine HCl on N balance in broiler breeder males fed 8% CP corn-based diets (3,220 kcal MEn/kg; .15% supplemental DL-methionine; .24% basal lysine). In Experiment 1, 78-wk-old males were fed the basal diet with either 0, .05, .10, or .25% supplemental L-lysine HCl. Birds were allowed to eat for 1 h each day to a maximum intake of 325 kcal MEn per bird per day. Total excreta were collected for 8 consecutive days. Nitrogen retention and balance were not different among treatments (P greater than .05) and responded neither linearly nor quadratically to dietary lysine level. Removing the variation due to differences in N intake with analysis of covariance did not change the response. In Experiment 2, 30-wk-old males were fed the same basal diet with supplemental lysine levels of 0, .15, .30, .45, .60, and .75% L-lysine HCl for 5 consecutive days. Nitrogen balance and retention were different among diets, and both variates responded linearly to increases in dietary lysine. Removing the variation due to differences in N intake removed treatment effects, however, suggesting that at least part of the difference was the result of variable levels of intake. Regression analysis indicated a significant linear increase in both N balance and retention with increasing dietary lysine level (R2 = .82). These results suggest that young broiler breeder males can make better use of the protein of corn if supplemental lysine is provided. However, older birds do not demonstrate improved N balance as a result of supplemental dietary lysine.