Dietary Bazhen San solid-state fermentation product improves laying performance, antioxidant capacity, and ovarian function in laying hens during the late laying period

This study investigated the effects of solid-state fermented Bazhen San (FB), prepared with Lactobacillus plantarum and Bifidobacterium animalis, on production performance and ovarian function in late-stage laying hens. A total of 120 seventy-week-old Jingfen laying hens were divided into four groups: a control group (CON) fed a basal diet, and three treatment groups supplemented with 0.3 % (LFB), 0.6 % (MFB), or 0.9 % FB (HFB). Pre-feeding for 2 weeks, and a formal experiment for 8 weeks. Results showed that from weeks 1 to 4, the MFB group exhibited a significantly higher laying rate than the CON group (P < 0.05). From weeks 5 to 8, all FB groups significantly increased laying rate and decreased the feed-to-egg ratio (P < 0.05). Up to week 8, compared with the CON group, the MFB and HFB groups showed significant improvement in shell strength, yolk color, and Haugh unit (P < 0.05). The MFB and HFB groups exhibited significantly increased follicle numbers and ovarian index compared to the CON group (P < 0.05). Production performance, egg quality, and follicular development all exhibited significant linear and quadratic responses to FB supplementation (P < 0.05). Meanwhile, the MFB group downregulated ovarian interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-α) (P < 0.05). All FB-supplemented groups exhibited enhanced antioxidant capacity compared to the CON group, with significant increases in serum CAT activity and T-AOC, as well as ovarian GSH-Px and SOD activities (P < 0.05). The MFB and HFB groups demonstrated a further enhancement of antioxidant capacity. Compared with the control group (CON), the levels of serum PROG and ovarian E2 significantly increased in each treatment group (P < 0.05). The improvements in inflammatory markers, antioxidant capacity, and reproductive hormones all showed significant linear and quadratic dose-response relationships with FB supplementation (P < 0.05). Transcriptome and KEGG pathway analysis of ovarian tissues showed that the PPAR signaling pathway was closely related to the improvement of egg production rate and antioxidant capacity. Therefore, supplementing FB in the feed of laying hens during the late stage of egg production can improve production performance and egg quality, and delays ovarian aging.