Grape seed and onion peel extracts improve laying performance, eggshell quality, and uterine function in aged laying hens

Prolonged laying cycles in ageing hens often result in reduced productivity, deteriorated egg quality, and uterine dysfunction, posing economic challenges. Proanthocyanidins (grape seed) and quercetin (onion peel) possess antioxidant and anti-inflammatory properties potentially mitigating age-related declines. This study evaluated dietary supplementation with a grape seed and onion peel extract (GOE: 40.4% proanthocyanidins and 11.5% quercetin) in aged laying hens. 62-week-old Hy-Line Grey hens were allocated to four groups: a control (basal diet) and groups supplemented with 160, 320, or 480 mg/kg GOE. After an 8-week trial, the low-dose GOE group (160 mg/kg) showed a significantly higher egg production rate and lower feed conversion ratio (FCR) than the control (p < 0.05), without altering ADFI or egg weight. 160 mg/kg GOE resulted in a 12.3% increase in eggshell strength, a 3.8% increase in thickness, a higher proportion of high-quality shells, and lower translucent egg scores (p < 0.05) compared to the control. These improvements were accompanied by elevated markers of uterine calcium transport (including serum calcium, uterine calcium content, and uterine calcium pump activity) along with a significant increase in uterine total antioxidant capacity (T-AOC; p < 0.05). Scanning electron microscopy (SEM) confirmed that low-dose GOE improved eggshell ultrastructure, while medium and high doses yielded inconsistent or lesser effects. The above results indicated that low-dose GOE supplementation effectively improved production efficiency, eggshell quality, calcium metabolism, and antioxidant status in aged laying hens. This strategy provides a practical nutritional approach to extend the productive lifespan and enhance egg quality in ageing flocks.