Bioavailability of the DL-methionine and the calcium salt of DL-methionine hydroxy analog compared with L-methionine for nitrogen retention in starter pigs.

Two nitrogen balance studies were conducted to evaluate the relative bioavailability values (RBV) of DL-Methionine (DL-Met) and DL-Methionine hydroxy analog calcium salt (MHA-Ca) to L-Methionine (L-Met) as Met sources fed to pigs. In Exp. 1, 42 pigs were assigned to 7 treatments feeding with basal diet (BD) formulated to be deficient in Met (0.22% standardized ileal digestible basis) but adequate in other amino acids. Diets included (1) BD, (2) BD + 0.025% DL-Met, (3) BD + 0.050% DL-Met, (4) BD + 0.075% DL-Met, (5) BD + 0.025% L-Met, (6) BD + 0.050% L-Met, and (7) BD + 0.075% L-Met. Increasing levels of L-Met and DL-Met enhanced N retained (g/d) and N retention (% of intake) linearly (P 0.05) on N retained (g/d) and N retention (% of intake). Using linear slope-ratio regression, the RBV of MHA-Ca compared to L-Met was 70% (95% confidence limits: 59 to 81%) on a product-to-product basis or 83% on equimolar basis based on N retained expressed as g/d. Overall, the mean RBV of DL-Met to L-Met of 97% (95% confidence limits cover 100%) indicated that DL-Met and L-Met are equally bioavailable as Met sources in pigs. Compared to L-Met, the RBV of MHA-Ca was lower at 70% (95% confidence limits: 59 to 81%) on a product-to-product basis or 83% on equimolar basis in starter pigs.