Abstract

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 g