Effects of Dietary Sterol-Enriched Yeast Hydrolysate on Ovarian Development, Reproductive Endocrine Status, Immune-Inflammatory Responses, Antioxidant Indices, and Egg Quality in Late-Laying Yellow-Feathered Broiler Breeder Hens

Abstract

This study evaluated graded dietary supplementation with sterol-enriched yeast hydrolysate (SYH) in late-laying yellow-feathered broiler breeder hens. A total of 720 55-week-old hens received 0, 0.2, 0.5, or 0.8 g/kg of SYH for six weeks after a one-week adaptation period. SYH is a composite product containing sterols, mannan, nucleotides, and amino nitrogen; therefore, the observed effects cannot be attributed to sterols alone. Eggshell strength increased at 0.5 and 0.8 g/kg, whereas fertility and hatchability were unaffected. The 0.5 g/kg group showed the highest ovarian index values and the greatest quantities of 5–12 mm yellow follicles. The 0.8 g/kg group showed the highest serum reproductive hormone and immunoglobulin concentrations, together with the highest reactive oxygen species and cytokine concentrations. Hepatic and ovarian superoxide dismutase activity increased selectively, whereas most other antioxidant indices were unchanged. Ovarian FSHR, CYP19A1, and VDR mRNA expression showed concentration-specific patterns. The strongest peripheral endocrine response at 0.8 g/kg did not coincide with the most favorable ovarian developmental response. Under the conditions of this study, 0.5 g/kg represents a candidate inclusion concentration for further validation rather than a confirmed optimum.