Effects of Dietary Supplementation of Omega-3 PUFA Enriched Fish Oil During Late-Pregnancy and Lactation on Reproductive Performance, Immune Activity and Fecal Microbiota Composition in Postpartum Sows

Delayed or failed postpartum estrus can impede the reproductive performance of rebreeding dams. Our study aimed to test whether dietary fish oil can promote estrus return and improve fecal microbiota in multiparous sows. Forty-five sows were randomly allocated into three treatments: a basal diet, or a basal diet plus 30 or 60 g/day of fish oil from gestation day 90 to lactation day 21. Results showed that dietary fish oil significantly elevated circulating DHA in sows, without significant changes in litter size, litter weight, or backfat loss. Supplementation of fish oil (30 or 60 g/day) shortened the interval from weaning to estrus by 1.8 days and 1.67 days, respectively, associated with a significant boost of estradiol. Increases in prolactin and IgA were only significant in the high-dosage group. In addition, plasma MDA and antioxidant activities were up-regulated by fish oil, combined with elevated serum IL-1β and IL-6. Moreover, dietary fish oil significantly reduced serum zonulin, improved the Simpson index of fecal microbiota, and increased the abundance of <i>Lactobacillus</i> and <i>Ruminococcaceae_UCG-014</i> genera. In conclusion, dietary omega-3 PUFA-enriched fish oil provides a promising approach to aiding estrus return and reshaping fecal microbiota in post-weaning sows.