Dietary supplementation of capsaicin on production performance, egg quality, follicle development and liver metabolism of late-phase Changshun green-shell laying hens

This study aimed to investigate the impacts of dietary capsaicin (CAP) on production performance, egg quality, follicle development, anti-oxidant capacity and lipid metabolism of laying hens at the late-period laying cycle. A total of 240 healthy Changshun green-shell late-phase laying hens were chosen and randomly allocated to three treatments, each consisted of 10 replicates with 8 hens per replicate. The hens in the control group were freely access to the basal diet and hens in the CAP group freely received diets containing 150 mg/kg CAP. While hens in the pair-feed (PF) group receiving the basal diet with amounts equal to those consumed the CAP diet on the previous day. The results showed that CAP supplementation increased egg mass and egg production of laying hens as well as improved egg yolk color and Haugh unit (P < 0.05). Furthermore, CAP supplementation reduced the concentrations of total cholesterol (TC), triglyceride (TG) and low-density lipoprotein cholesterol (LDL-C) in plasma (P < 0.05). But CAP supplementation elevated the concentrations of follicle stimulating hormone releasing hormone (FSH), luteinizing hormone (LH), progesterone (P4) and Estradiol (E2) in serum (P < 0.05). CAP addition downregulated mRNA expressions of acetyl-CoA carboxylase (ACC), fatty-acid synthase (FAS), sterol regulatory element binding protein-1 (SREBP1) and liver X receptors (LXRs, P < 0.05) in liver. In addition, CAP addition increased the abundances of Bacillota, Actinomycetota, and Puseudomonadota in the cecum of laying hens (P < 0.05). Besides, the concentrations of propionic acid, butyric acid, isobutyric acid and caproic acid were higher in the CAP group (P < 0.05). Additionally, CAP also upregulated mRNA expressions of transient receptor potential cation channel subfamily V member 1 (TRPV1), calmodulin (CaM), follicle stimulating hormone receptor (FSHR) and luteinizing hormone receptor (LHR) in ovary (P < 0.05) and downregulated related mRNA expressions involved in lipid metabolism in the liver of layers (P < 0.05). Collectively, these results demonstrated that CAP supplementation could increase the production performance, improve egg quality, promote follicle development of late-phase laying hens by altering cecal microbiota and metabolism, liver lipid metabolism and oviduct function.