Bioefficacy of L-lysine sulfate compared to feed grade lysine·HCl in young pigs

A pig growth assay was conducted to determine the relative biological value (RBV) of lysine from L-lysine sulfate relative to feed grade lysine·HCl. A maize-peanut meal diet containing 6.2 g/kg total lysine was supplemented with 2 levels (1 and 2 g/kg) of lysine from L-lysine·HCl or L-lysine sulfate. The RBV of L-lysine sulfate was determined using multiple regression slope-ratio methodology, with gain and feed efficiency as the response criteria. At the tested levels, linear responses for gain and feed efficiency were obtained from increments of lysine from the two lysine sources. When weight gain was regressed on supplemental lysine intake, the RBV of lysine in L-lysine sulfate was 99% of the RBV of lysine in L-lysine·HCl. For feed efficiency was regressed on supplemental lysine intake, the RBV of lysine in L-lysine sulfate was 97% of the RBV of lysine in L-lysine·HCl. The t-test analysis revealed that the RBV of lysine in L-lysine sulfate was not significantly different from the RBV of lysine in L-lysine·HCl, which was assumed to be 100% bioavailable.