Dietary chlorogenic acid improves sperm kinematics in aging breeder roosters via modulation of the Nrf2-mediated antioxidant pathway

This study investigated the effects of dietary chlorogenic acid (CGA) supplementation on sperm motility parameters, antioxidant capacity, and reproductive hormone levels in aging breeder roosters. Ninety-six 63-week-old Jingfen No. 6 roosters were randomly divided into four groups and fed diets supplemented with 0, 500, 1000, and 2000 mg/kg CGA for six weeks. Dietary CGA supplementation significantly improved sperm motility parameters, including straight-line velocity (VSL), curvilinear velocity (VCL), average path velocity (VAP), straightness (STR), and linearity (LIN) ( P < 0.05), with most parameters increasing linearly with increasing CGA supplementation ( P < 0.01). The 2000 mg/kg group generally had the highest sperm velocity and motility characteristics at week 6. CGA supplementation significantly affected plasma concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and testosterone (T) ( P < 0.05), with the highest levels observed in the 500 mg/kg group. CGA significantly enhanced the antioxidant capacity of plasma, seminal plasma, and testicular tissue, manifested by increased activities of superoxide dismutase (SOD) and catalase (CAT), as well as enhanced scavenging capacity for superoxide anions and hydroxyl radicals ( P < 0.05). Simultaneously, malondialdehyde (MDA) levels were significantly reduced in all CGA-supplemented groups ( P < 0.05), indicating reduced lipid peroxidation. At the molecular level, CGA supplementation upregulated nuclear factor erythroid 2-related factor 2 (Nrf2) and several antioxidant-related genes. Specifically, glutathione peroxidase 4 ( GPX4 ) expression was significantly increased in all CGA-treated groups, whereas superoxide dismutase 2 ( SOD2 ) and CAT expression were significantly elevated in the 2000 mg/kg group. In addition, Nrf2 expression was significantly increased in the 500 and 2000 mg/kg groups ( P < 0.05). In conclusion, dietary supplementation with CGA improved sperm motility and enhanced antioxidant capacity in aging layer breeder roosters, and these beneficial effects may be associated with enhanced antioxidant defense mediated, at least in part, through the Nrf2-related signaling pathway. These findings suggest that CGA is a promising functional feed additive for improving the reproductive performance of aging roosters.