Kaempferol supplementation at 150 mg/kg improves reproductive performance of aged laying hens via modulation of the gut-liver-ovary axis.

The decline of egg production in aged laying hens is primarily due to age-related declines in hepatic and ovarian functions as well as changes in reproductive hormones and reduced antioxidant capacity. Kaempferol (KAE), a flavonoid compound with potent antioxidant activity also affects ovarian functions in mammals, but its role in chickens remains poorly understood. We aimed to investigate the potential of KAE to mitigate reproductive decline in aged laying hens through modulation of the gut-liver-ovary axis. A total of 400 Hy-Line Brown aged laying hens (420 days old) were randomly assigned to four groups consistent of five replicates with 20 hens per replicate and fed diets supplemented with either 0, 75, 150, or 300 mg/kg KAE. Dietary KAE significantly improved villus height and the villus height-to-crypt depth ratio in the duodenum, jejunum, and ileum.The mRNA expression of intestinal barrier-related genes (ZO-1, claudin-1, mucin, and occludin) were increased by dietary KAE, and partially enhanced intestinal absorption and barrier function. KAE also improved hepatic morphology, reduced hepatic triglyceride (TG) and total cholesterol (TC) levels, and significantly increased the expression of lipid synthesis and transport-related genes (FAS and MTTP). Moreover, the expression of yolk precursor synthesis-related genes including VTG-II, ApoVLDL-II, VLDLR, ER-α, ER-β, and PPAR-α were upregulated by KAE. Dietary KAE was effective in elevating the level of estradiol (E2), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and progesterone (P4), and upregulating the mRNA transcripts of ER-α, ER-β, FSHR, and LHR in ovary. Additionally, KAE was effective in enhancing the ovarian antioxidant capacity, while reducing reactive oxygen species (ROS) accumulation, and inhibiting apoptosis in prehierarchical follicles. In conclusion, 150 mg/kg KAE is the optimum dose improving intestinal integrity and hepatic metabolism, promoting follicular development and steroid hormone secretion, and ultimately enhancing egg production performance by modulating the gut-liver-ovary axis in aged laying hens.