Maternal Tryptophan Supplementation Enhances Sow Reproductive Performance by Influencing Hormones, Tryptophan Metabolism, and Gut Microbiome.

Background: Enhancing the early embryo survival rate is important for increasing sow reproductive efficiency. Whether and how tryptophan influences early embryo survival and pregnancy outcomes in sows remains unknown.

Objectives: The objective of this study was to investigate the effects of dietary tryptophan supplementation on the reproductive performance of sows.

Methods: A total of 128 multiparous Large White × Landrace sows were randomly assigned to 4 groups including the control group (dietary tryptophan concentration was 0.18% from weaning to estrus and 0.10% from day 1 to day 28 of pregnancy) or the low, medium, and high dose of tryptophan supplementation groups (dietary tryptophan levels were 0.27%, 0.36%, and 0.45% from weaning to estrus and 0.15%, 0.20%, and 0.25% from day 1 to day 28 of pregnancy). Primary porcine granulosa cells were isolated from porcine ovaries and treated with selected tryptophan metabolites to assess hormone levels in the cell supernatant.

Results: Compared with the control group, the dietary high levels of tryptophan group increased the litter weight (P < 0.05) and showed an increasing trend in the born alive per litter (P = 0.06). Serum concentration of progesterone and estradiol and levels of tryptophan, kynurenine, xanthurenic acid, 2-aminobenzoic acid, and indoleamine 2,3-dioxygenase on day 28 of pregnancy were increased in the high concentration of tryptophan group (P < 0.05). In vitro experiments using primary porcine granulosa cell culture showed that tryptophan and 2-aminobenzoic acid increased progesterone and estradiol levels in the cell supernatant (P < 0.05). Dietary tryptophan supplementation increased the abundances of fecal beneficial bacteria such as Hydrogenoanaerobacterium and Lachnospiraceae in sows (P < 0.05).

Conclusions: Dietary tryptophan supplementation may enhance the pregnancy outcome of sows through the increase of tryptophan metabolites to strengthen steroid hormone secretion and the abundance of beneficial microbes.