Bioefficacy of L-lysine.H2SO4 relative to L-lysine.HCl in broiler chickens, estimated by slope-ratio model.

1. A broiler experiment was conducted to assess the effectiveness of L-lysine.H2SO4 relative to L-lysine.HCl. Four concentrations of L-lysine.H2SO4 and L-lysine.HCl (0.9, 1.8, 2.7 and 3.6 g/kg diet) were each added to a basal diet that met the nutrient requirements of broilers except for lysine. 2. Birds responded significantly to the supplements in daily gain, feed intake, feed conversion efficiency, nitrogen retention and plasma urea nitrogen during each period (d 4 to 21, d 22 to 42 and d 4 to 42). 3. Regression analysis showed that the bioefficacy of L-lysine.H2SO4 relative to L-lysine.HCl was 0.93, 0.86 and 0.95 for daily gain, feed conversion efficiency and nitrogen retention, respectively, during the starter period (d 4 to 21), and was 1.01, 1.36 and 1.06, respectively, during the grower period (d 22 to 42). It was 0.99, 1.07 and 1.03, respectively, for the overall period (d 4 to 42), when the bioefficacy of L-lysine.HCl was set at 1.0. 4. The bioefficacy of L-lysine.H2SO4 differed with different response criteria. The average bioavailability of L-lysine.H2SO4 relative to L-lysine.HCl was 1.03 on an equimolar basis in the present study. In conclusion, L-lysine.H2SO4 and L-lysine.HCl are equally efficacious to broiler chickens.