361. Effects of Dietary Medium-chain Fatty Acid Supplementation Levels on Growth Performance, Fecal Score, Energy, Antioxidant, and Inflammatory Status of Nursery Pigs Fed High Protein Diets.

Abstract This study evaluated the effects of increasing medium-chain fatty acid (MCFA) supplementation levels on growth performance, fecal score, energy, antioxidant, and inflammatory status in nursery pigs fed high protein diets. A total of 72 pigs (initial body weight: 6.68 ± 0.97 kg weaned at 17.0 ± 3.02 d of age) were allotted to 3 treatments in 6 replicates, with 4 pigs per pen for a 35-d feeding trial. Treatments were diets with MCFA supplementation levels at 0.0%, 0.5%, and 1.0%, replacing soybean oil accordingly with two phases of d 0-21 (Phase 1) and d 21-35 (Phase 2) postweaning. Growth performance and fecal score (1=normal, 4=severe diarrhea) were measured in weekly and overall period. Blood samples were collected on d 7 and 21 postweaning and fecal samples were collected on d 21 and 35 postweaning. Linear and quadratic effects were analyzed for increasing MCFA levels. With increasing MCFA levels, average daily gain linearly increased in d 21-28 (P < 0.05) and 21-35 (P = 0.08, tendency; 0.605, 0.653, and 0.651 kg/d, respectively) postweaning, average daily feed intake linearly decreased in d 0-21 postweaning (P < 0.05; 0.459, 0.420, and 0.400 kg/d, respectively), and gain-to-feed ratio quadratically increased in d 0-21, 21-35 postweaning and overall period (P < 0.05; 0.607, 0.685, and 0.670, respectively), while fecal score linearly decreased in d 0-21 postweaning and overall period (P < 0.05; 1.48, 1.42, and 1.28, respectively). There were no differences in serum superoxide dismutase activity, protein carbonyl and malondialdehyde levels. Serum urea nitrogen linearly increased with increasing MCFA levels at d 7 (P < 0.05) and 21 postweaning (P = 0.08; 6.83, 8.00, and 8.17 mg/dL, respectively), while serum free fatty acid levels linearly decreased at d 21 postweaning (P < 0.05; 302.37, 278.70, and 244.26 µM, respectively). Serum IL-1β (P = 0.10; 355.78, 271.48, and 237.79 pg/mL, respectively) and IL-8 (P = 0.06; 176.71, 92.58, and 74.86 pg/mL, respectively) tended to decrease linearly with increasing MCFA levels at d 7 postweaning. Increasing MCFA levels decreased serum d-lactate levels linearly at d 7 postweaning (P < 0.05; 0.49, 0.47, and 0.31 mM) and tended to decrease serum diamine oxidase levels at d 7 (P = 0.09, linear) and 21 (P = 0.06, quadratic; 32.97, 28.29, and 30.95 ng/mL, respectively) postweaning. Although fecal acetate concentrations tended to linearly decrease with increasing MCFA levels (P = 0.06; 75.38, 72.21, and 60.36 mM, respectively) at d 21 postweaning, there were linear increases in fecal propionate and butyrate concentrations (P < 0.05; 12.5, 16.35, and 20.32 mM, respectively). In conclusion, MCFA supplementation up to 1.0% in high-protein diets enhanced growth rate, feed efficiency, fecal consistency, energy status, gut integrity, immune function, and fecal butyrate concentrations in nursery pigs, although early nursery feed intake was slightly reduced, potentially due to satiety effects of MCFAs.