Effect of feed grade L-methionine on growth performance and gut health in nursery pigs compared with conventional DL-methionine

Two experiments were conducted to test if supplementation of LMET has beneficial effects on growth performance and gut health in nursery pigs compared with DL-Met. In Exp. 1, 168 pigs in 56 pens were randomly allotted to 7 dietary treatments for 20 d, including a basal diet (BD; 55% of the NRC requirement for Met), the BD + 0.048% L-Met or DL-Met (70% of the NRC requirement), the BD + 0.096% L-Met or DL-Met (85% of the NRC requirement), and the BD + 0.144% L-Met or DL-Met (100% of the NRC requirement). Body weight and feed disappearance were recorded every 5 d for computation of growth performance. In Exp. 2, 20 individually housed nursery pigs were randomly allotted to 2 dietary treatments for 20 d: DML (0.16% Met from the BD + 0.145% supplemental DL-Met) or LMET (0.16% Met from the BD + 0.145% supplemental L-Met). Both diets had Met meeting 95% of the NRC requirement. Duodenum samples from all pigs were collected at the end of the trial to evaluate morphology and redox status. In Exp. 1, during the entire 20 d, pigs fed diets supplemented with L-Met tended to have greater (P = 0.087) ADG and reduced (P < 0.01) plasma urea nitrogen (PUN) than pigs fed diets supplemented with DL-Met. The relative bioavailability (RBA) of L-Met to DL-Met for ADG and G: F was 143.8 and 122.7%, respectively. In Exp. 2, pigs fed a diet supplemented with L-Met had duodenum tissue with greater (P < 0.05) concentrations of glutathione (GSH) and greater villus height and width as well as lower (P < 0.05) concentrations of protein carbonyl compared with pigs fed DL-Met. Overall, compared with dlMet, the use of L-Met as a source of supplemental Met in nursery pig diets enhanced duodenum villus development in association with reduced oxidative stress and improved GSH. The beneficial effects of supplementing L-Met compared to DL-Met in gut of nursery pigs resulted in a potential enhancement of ADG and reduction of PUN.