Investigating the Effects of Dietary Bile Acids on Production Performance and Lipid Metabolism in Late-Phase Laying...

Multiply adverse effects including declines in production performance and excessive fat deposition were noticed with the extension of the laying cycle in hens, which are pertinent to animal welfare and human food safety. This study aimed to investigate the effect of dietary supplementation of bile acids (BAs) on production performance and lipid metabolism in late-phase laying hens. A total of 144 70-week-old hens were distributed into three treatments with eight replicates per treatment, including the basal diet with 0 (Ctrl), 95.01 (Low-BA), and 189.99 mg/kg (High-BA) of porcine BAs, respectively. The test period was from 70 to 75 weeks. The supplementation of BAs did not significantly alter laying performance during the trial, whereas it increased (p < 0.05) the total follicles compared to the Ctrl diet. The eggs from the hens fed the BA diet exhibited increased (p > 0.05) relative weight of eggshell and yolk color than those that consumed the Ctrl diet. There were no significant changes following BA treatment regarding the serum lipid profile. Dietary BA treatment reduced the total triglyceride in livers to different extents, resulting in the decreased diameter and area of vacuoles in liver tissues. The low-dose BA treatment decreased the mRNA levels of fatty acid synthase (FASN) and stearoyl-CoA desaturase (SCD), while promoting the expression of lipoprotein lipase (LPL) compared to the Ctrl group (both p < 0.05). Of note, the expressions of farnesoid X receptor (FXR), apical sodium-dependent bile acid transporter (ASBT), and ileum bile acid-binding protein (IBABP) were notably downregulated (p < 0.05) by the low-dose BA treatment. Dietary BA treatment had no apparent effects on laying performance, whereas it increased the follicle frequency, eggshell weight, and yolk color. Moreover, a diet containing 95.01 mg/kg of BAs depressed ileal BA resorption and hepatic fatty deposition by reducing lipogenesis and promoting lipolysis, which may have a beneficial effect on the liver in late-phase layers.