Effects of Dietary Kelp Enzymatic Hydrolysate Supplementation on Performance, Antioxidant Capacity, Immune Function, and Intestinal Health of Sows and Their Piglets

This study is the first to investigate the effects of dietary supplementation with kelp enzymatic hydrolysate (KEH) from day 85 of gestation to day 21 of lactation in sows. Twenty-four Landrace × Yorkshire sows were randomly assigned to four treatments: a control diet (0% KEH) and three experimental diets supplemented with 0.75%, 1.50%, or 3.00% KEH. Backfat thickness at 24 h postpartum increased linearly with KEH supplementation (p = 0.02), while the number of piglets born alive showed a quadratic response (p = 0.03). KEH linearly increased glutathione peroxidase activity in umbilical cord blood (p = 0.02) and quadratically affected catalase activity in 21-day-old piglets (p = 0.02), which peaked at 1.50% KEH. Concentrations of immunoglobulin A (IgA; p = 0.01) and M (IgM; p = 0.02) in umbilical cord blood were quadratically enhanced by KEH, peaking at 1.50% and at 0.75% KEH, respectively. Serum IgG in 7-day-old piglets and IgM and IgG in 21-day-old piglets were linearly and quadratically influenced by KEH (p < 0.05). Quadratic responses were observed in serum triiodothyronine (p = 0.03) and interleukin-1β (p < 0.01) in 7-day-old piglets, as well as in serum interleukin-6 in 21-day-old piglets (p < 0.01). KEH had linear and quadratic effects in interleukin-1β in 14- and 21-day-old piglets (p < 0.05). Quadratic tendencies were detected in fecal acetic acid concentration in sows (p = 0.09) and in fecal isobutyric acid (p = 0.06) and isovaleric acid (p = 0.07) content in piglets, whereas the fecal valeric acid concentration in piglets was quadratically affected (p = 0.02) by KEH. Intestinal Firmicutes and Bacteroidota were the dominant phyla, with Lactobacillus being the most dominant genus in both sows and piglets. In piglets, Holdemanella was positively correlated with several short-chain fatty acids (SCFAs). Overall, dietary 0.75–1.50% KEH during late gestation and lactation improved reproductive performance, immune and antioxidant capacity, inflammatory status, and intestinal SCFA profiles in both sows and their offspring.