Combined supplementation of essential oils, Saccharomyces cerevisiae and isomaltooligosaccharides improves intestinal absorption and immune functions in weaned piglets.

This study evaluated the synergistic effects of essential oils (EOs), Saccharomyces cerevisiae (SC), and isomaltooligosaccharides (IMO) on intestinal health and systemic immunity in weaned piglets using a randomized block design across two commercial farms. Within each farm, 108 piglets weaned at 24 d of age were randomly divided into 3 groups (3 pens per group, 12 piglets per pen). The piglets were fed a basal diet (CON) and a basal diet supplemented with antibiotics (0.5 kg/t colistin sulfate + 0.5 kg/t tilmicosin) (ANTI) or additive mixture (0.1 kg/t EOs, 0.3 kg/t SC and 1 kg/t IMO) (ESI) for 28 days. The results showed that both ESI and ANTI treatments significantly increased the ratio of villus height to crypt depth (P < 0.05). Specifically, ESI supplementation elevated serum IgA, hepatic IgA, and jejunal mucosal sIgA levels (P < 0.05), while upregulating hepatic IL1B, IL2, IL6, and IFNG expression alongside jejunal mucosal IL1B, IL6, and PPARG expression-contrasting with its downregulation of jejunal mucosal IFNG mRNA (P < 0.05). Conversely, compared with the CON group, ANTI supplementation increased serum IgA level and jejunal mucosal concentrations of sIgA, IgG, IgM, IFN-γ, and IL-10, while also upregulating jejunal mucosal gene expression of IGF1 and TGFB1 (P < 0.05). In addition, compared with Farm I, piglets at Farm II exhibited higher jejunal pH, elevated serum levels of IgA and IL-1β, and upregulated gene expression of IL1B, IL2, IL6, and IFNG in the liver as well as TGFB1, IL1B, IL6, and PPARG in the jejunal mucosa (P < 0.05). Moreover, the robust diet × farm interaction effects on immune gene expression in the liver (IL1B, IL2, and IL6) and jejunal mucosa (IL1B, IL2, IL6, IFNG, IL10, and PPARG) were observed (P < 0.05). Collectively, ESI improved jejunal epithelial maturation, nutrient absorption, and immune function in weaned piglets, with efficacy partly dependent on farm environmental conditions.