Effects of medium-chain fatty acid supplementation levels in early nursery diets on growth performance, fecal score, gut permeability, energy status, and apparent total tract digestibility of weaning pigs.

This study was conducted to evaluate the effects of dietary medium-chain fatty acid () levels on growth performance, fecal score, gut permeability, energy status, and apparent total tract digestibility () of weaning pigs. At weaning, a total of 100 pigs [18.4 ± 1.8 d of age; initial body weight () of 5.72 ± 1.4 kg] were allotted to 5 treatments in 5 replicates with 4 pigs per pen for a 35-d feeding trial. Treatments were dietary MCFA levels of 0.0, 0.2, 0.5, 1.0, and 1.5% for d 0 to 21 postweaning (Phase 1) replacing soybean oil and a common nursery diet was fed to all pigs for d 21 to 35 postweaning (Phase 2). With increasing dietary MCFA levels, quadratic increases were observed in BW ( ≤ 0.05), average daily gain (;  ≤ 0.05), and average daily feed intake (;  = 0.08, tendency) in d 0 to 14 postweaning, peaking at the 0.5% MCFA level. The BW from d 21 to 35 postweaning and ADG in d 0 to 21 and 21 to 35 postweaning increased linearly with increasing MCFA levels ( ≤ 0.05), while linear and quadratic increases were observed in overall ADG ( ≤ 0.05), with the greatest value observed at the 1.0% MCFA level. The ADFI increased linearly ( ≤ 0.05) with increasing MCFA levels in d 21 to 35 postweaning and overall period, while gain-to-feed ratio was not different in each phase and overall period. Fecal score was not affected in the overall period ( > 0.21). The ATTD of gross energy ( ≤ 0.05), dry matter ( = 0.10, tendency) and crude protein ( = 0.07, tendency) increased linearly with increasing MCFA levels. At d 7 postweaning, plasma β-hydroxybutyrate levels decreased linearly ( = 0.06, tendency) with increasing MCFA levels, while plasma free fatty acid levels showed a quadratic response ( = 0.06, tendency) with the lowest levels at the 0.5% MCFA level. Increasing MCFA levels decreased plasma diamine oxidase levels at d 7 postweaning ( = 0.06, tendency), while showing quadratic decreases in plasma d-lactate levels at d 7 ( ≤ 0.05) and 21 ( = 0.10, tendency) postweaning, with lower values observed at the 0.2% to 1.0% MCFA levels compared to the 0.0% MCFA level. In conclusion, increasing dietary MCFA levels up to 1.0% enhanced overall growth rate and feed intake, energy and protein digestibility in nursery pigs, improved energy status by lowering plasma β-hydroxybutyrate and free fatty acid levels, and reduced gut permeability in the early nursery period.