The Effect of Increasing Total Sulfur Amino Acids to Lysine Level and Methionine Source on Growth Performance and Oxidative Parameters of Nursery Pigs Fed Oxidized Soybean Oil

Abstract Total sulfur amino acids (TSAA): Lys level and Met source effects on growth performance and oxidative status were evaluated in nursery pigs fed oxidized soybean-oil. A total of 240 weaned pigs (BW=5.84± 0.96kg) were blocked by BW and randomly allotted to 60 pens. Treatments included a positive control containing fresh soybean-oil (PC) and 4 peroxidized soybean-oil treatments in a 2×2 factorial of 2 Met sources (DL-Met vs. 2-hydroxy-4-(methylthio)butanoate [HMTBa]) and 2 standardized ileal digestible TSAA: Lys levels (L1=0.58 vs. L2=0.65). Diets were fed for 42d. One pig per pen was euthanized at d42 for tissue analyses. Data were analyzed using PROC MIXED procedure of SAS. TSAA: Lys ratio did not affect ADG and ADFI. Met source did not affect ADG. HMTBa tended to increase ADFI compared to DL-Met (P = 0.08). There was a tendency for interaction between TSAA: Lys level and Met source for G: F (P = 0.07); pigs fed HMTBa-L1 tended to have decreased G: F compared to HMTBa-L2 and DL-Met-L1-L2. HMTBa had increased liver total antioxidant status (TAS) compared to DL-Met (P = 0.02). There was no TSAA:Lys level effect on TAS. Comparing PC to peroxidized treatments: pigs fed HMTBa-L1 and DL-Met-L1 tended to have decreased ADG (P ≤ 0.10) and DL-Met-L2 had decreased ADG (P < 0.05) than PC. HMTBa-L2 was similar to PC. Pigs fed DL-Met-L1 had decreased (P < 0.05) and DL-Met-L2 tended to have decreased ADFI (P ≤ 0.10) than PC. HMTBa-L1-L2 were similar to PC. All peroxidized treatments had similar G:F compared to PC. Pigs fed DL-Met-L2 tended to have decreased TAS compared to PC (P ≤ 0.10), but PC was similar to pigs fed DL-Met-L1 and HMTBa-L1-L2. In conclusion, under an oxidative challenge, HMTBa, at a TSAA: Lys ratio of 0.65, maintained nursery pigs’ growth performance and oxidative status.