Effects of dietary medium-chain fatty acid supplementation levels on growth performance, fecal score, energy, antioxidant, inflammatory status, and fecal metabolites of nursery pigs fed high-protein diets

This study evaluated the effects of increasing medium-chain fatty acid (MCFA) supplementation levels on growth performance, fecal score, energy status, gut health, inflammatory responses, and fecal metabolites in nursery pigs fed high-protein diets (24-24.5% crude protein; CP). A total of 72 pigs (initial body weight: 4.89 ± 1.57 kg weaned at 17.8 ± 2.35 d) were allotted to 3 treatments in 6 replicates, with 4 pigs per pen for a 35-d feeding trial. Treatments were based on MCFA supplementation levels at 0.0%, 0.5%, and 1.0%, with two phases of d 0 to 21 (Phase 1, 24% CP) and 21 to 35 (Phase 2, 24.5% CP) postweaning. Growth performance and fecal score (1 = normal, 4 = severe diarrhea), blood parameters at d 7 and 21 postweaning and fecal short-chain fatty acid (SCFA) levels at d 21 and 35 postweaning were measured. With increasing MCFA levels, average daily gain linearly increased in d 21 to 28 (P < 0.05) and 21 to 35 (P = 0.08, tendency) postweaning, average daily feed intake linearly decreased in d 0 to 21 postweaning (P < 0.05), and gain-to-feed ratio quadratically increased in d 0 to 21, 21 to 35 postweaning, and overall period (P < 0.05), while fecal score linearly decreased in d 0 to 21 (P < 0.05), and d 21 to 35 (P = 0.09, tendency) postweaning, and overall period (P < 0.05). Serum free fatty acid levels decreased linearly at d 21 postweaning (P < 0.05), while serum interleukin-1β and interleukin-8 tended to decrease linearly with increasing MCFA levels at d 7 postweaning (P < 0.10). Serum urea nitrogen linearly increased with increasing MCFA levels at d 7 (P < 0.05) and 21 (P = 0.08, tendency) postweaning, while serum d-lactate levels decreased quadratically at d 21 postweaning (P < 0.05) and serum diamine oxidase levels tended to decrease at d 7 (P = 0.09, linear) and 21 (P = 0.06, quadratically) postweaning. There were no differences in serum superoxide dismutase activity, protein carbonyl and malondialdehyde levels. Fecal propionate, butyrate and total SCFA concentrations increased linearly with increasing MCFA levels at d 35 postweaning (P < 0.05). In conclusion, dietary MCFA supplementation up to 1.0% in high-protein diets could improve growth rate, feed efficiency, and fecal consistency in the nursery period and enhance energy status, gut integrity, immunity, and fecal SCFA concentrations in nursery pigs although a slight reduction in feed intake was observed in early nursery period, potentially due to its satiety effects.