Effects of Dietary Supplementation of DL-Methionine or DL-Methionine Hydroxyl Analogue (MHA-Ca) on Growth Performance and Blood and Liver Redox Status in Growing Pigs

Oxidative stress impairs pigs' health and production performance. This study examined the effects of level and source of methionine (Met) supplementation against the diquat-induced oxidative stress in pigs. Forty growing barrows were randomly assigned to four groups. Groups 1 and 2 received a basal diet that was adequate in energy and nutrients (Diet 1), Group 3 received a DL-Met-supplemented diet, and Group 4 received an MHA-Ca-supplemented diet. After 3 weeks of feeding (Phase 1), pigs were injected with 10 mL saline (Group 1) or 10 mg/kg-BW diquat in 10 mL saline (Groups 2, 3, and 4), and then continually fed for one week (Phase 2). During or at the end of Phase 1, there were no differences in nearly all of the growth performance and redox parameters among the four groups. During or at the end of Phase 2, however, the ADFI and ADG were lower (<i>p</i> < 0.01) in Group 2 than in Group 1 while the serum malondialdehyde content was higher (<i>p</i> < 0.05) in Group 2 than in Group 1. The serum glutathione peroxidase (GPX) activity and liver superoxide dismutase (SOD) activity were lower (<i>p</i> < 0.05) in Group 2 than in Group 1. The serum GPX activity, the serum total antioxidant capacity, and the liver GPX activity were higher (<i>p</i> < 0.05) in Group 3 than in Group 2. There were nearly no differences in these redox parameters between Groups 3 and 4. In conclusion, MHA-Ca and DL-Met, when used at an equivalent bioefficacy level, had similar effects on the pigs' growth performance and antioxidative status. Therefore, increased Met supplementation can improve pigs' antioxidative status.