Positive effects of bile acids alleviating heat stress in laying hens by enhancing immunity via metabolome and transcriptome integration.

This experiment was aimed to investigate the effects of dietary supplementation with porcine-derived bile acids (BAs) on production performance, immune function, serum metabolome, and liver transcriptome in heat-stressed laying hens. A total of 400 55-week-old Jingfen No.3 laying hens with similar body weight and laying rate were randomly allocated to 5 groups (8 replicates/group, 10 hens/replicate): normal temperature control group (CON, 26 ± 1°C, basal diet), high temperature control group (HS, 35 ± 1°C, basal diet), and three high-temperature BA-supplemented groups (HT, 35 ± 1°C, basal diet + 60, 120, or 240 mg/kg BAs). The CON group was maintained at normal temperature throughout the experiment, while the HS and HT groups were subjected to a cyclic temperature regime of 16 h high temperature/8 h normal temperature for 28 days. Compared with the CON group, the HS group showed significantly decreased laying rate, average egg weight, average daily feed intake, total egg mass, serum immunoglobulin A (IgA), immunoglobulin G (IgG), interleukin-10 (IL-10) levels and spleen index (P < 0.05), along with significantly increased serum corticosterone (CORT), heat shock protein 70 (HSP70), and interleukin-1β (IL-1β) contents (P < 0.05). Dietary supplementation with 120 mg/kg BAs significantly improved laying rate and total egg mass (P < 0.05), reduced serum CORT, HSP70, IL-1β and liver index levels (P < 0.05), and increased serum IgA, immunoglobulin M (IgM) levels and spleen index (P < 0.05) compared with the HS group. Serum metabolomics identified 129 differentially accumulated metabolites (DAMs), mainly including prostaglandin A₂ (PGA₂), 5,6-dihydroxyeicosatrienoic acid (5,6-DHET), 11,12,15-trihydroxyeicosatrienoic acid (11,12,15-THETA), and arachidonate. Liver transcriptomics revealed 347 differentially expressed genes (DEGs), primarily involving major histocompatibility complex class I (MHC I), interleukin-2 receptor (IL-2R), transforming growth factor-β receptor (TGF-βR), and multivesicular body protein 12A (MVB12A). Spearman correlation analysis indicated that IgA was significantly positively correlated with 11,12,15-THETA but significantly negatively correlated with arachidonate; IgM was significantly positively correlated with both 11,12,15-THETA and 5,6-DHET. Furthermore, 5,6-DHET was significantly positively correlated with MVB12A and IL-2R, and 11,12,15-THETA was also significantly positively correlated with MVB12A; arachidonate was significantly negatively correlated with MVB12A and TGF-βR. In conclusion, dietary supplementation with 120 mg/kg porcine-derived BAs can improve production performance by enhancing immune function in heat-stressed laying hens.