Inclusion of a fish oil processing fraction as additive in diets for weaning piglets

Abstract

The weaning process in pig production is commonly associated to low feed intake, slow growth rate and increased morbidity of piglets. This study evaluates a nutritional intervention consisting of supplementing with a fish oil product rich in mono- and diglycerides (FOMG) and containing 0.069 g/g of ω-3, to improve animal health and productive performance during the post-weaning period. In a preliminary experiment (experiment 1), a total of 136 piglets were randomly distributed in two groups (4 pens per group) to evaluate the productive effects of dietary supplementation with FOMG at 15 g/kg (T15) in substitution of lard (T0) as fat source during the post-weaning period in a commercial farm. Besides, in experiment 2 a total of 72 weaned piglets were fed on a control diet (T0) or supplemented with 15 (T15) or 30 g FOMG/kg (T30) in substitution of sunflower oil, with 6 pens of 4 piglets per treatment. In experiment 2 growth and intake were weekly controlled, and blood was sampled on days 14 and 34. At day 35 post-weaning, 6 piglets per treatment were euthanized to study the microbial fermentation and the ileal and caecal bacterial community by 16 S amplicon sequencing. Results indicated that piglets fed T15 diet tended to have a higher growth gain during the post-weaning period in experiment 1 (P = 0.067). This increased growth was partially explained by a greater feed intake (0.14 higher) but also due to improved animal health as showed by the lower proportion of neutrophils (P = 0.006), blood cortisol (P = 0.098) and morbidity (P < 0.05) in experiment 2. Treatment T15 also tended (P = 0.064) to promote a higher volatile fatty acids (VFA) concentration at the ileum, which could be compatible with a higher nutrient absorption and a subsequent lower VFA concentration in the hindgut (P < 0.001). Moreover, FOMG supplementation at T15 exerted modulatory effects on the gut microbiota promoting a shift in the bacterial community structure, lower diversity (Richness index, P < 0.05) and a trend (P = 0.076) for a higher butyrate proportion at the ileum, together with a lower (P < 0.05) and most favourable Firmicutes-to-Bacteroidetes ratio at the caecum. On the contrary, T30 diet promoted less beneficial effects than T15. These findings indicated that supplementation of piglets with FOMG at a level of 15 g/kg represents a suitable strategy to improve pig performance and gut health during the post-weaning period.