Orange corn diet decreased serum corticosterone and improved gait, egg production, egg quality and fertility of breeder Pekin ducks exposed to heat stress.

Heat stress (HS) impairs poultry performance and welfare, necessitating effective mitigation strategies. Carotenoids exhibit antioxidant properties that may enhance thermotolerance. This study evaluated whether a high-carotenoid orange corn (OC) diet could mitigate the effects of HS in breeder Pekin ducks compared to a standard yellow corn (YC) diet. A total of 224 hens and 56 drakes were randomly assigned to OC or YC diets (n = 4 pens/diet) for 3 weeks prior to and during 3 weeks of cyclic HS (35 °C/10 h daily). Weeks -3, -2, -1, 0, 1, 2, and 3 represent 3 weeks before and 3 weeks of HS respectively. Blood samples (n = 8/sex/diet/timepoint) were collected at weeks -3 and -2, and at 4 h, 48 h, and 1, 2, and 3 weeks of HS. Body weight (BW), feed intake (FI), egg production, egg quality (n = 40 eggs/diet/timepoint), and transect walk assessment were evaluated weekly. Fertility and hatchability were assessed at the end of HS. Hen serum corticosterone was lower in OC compared to YC hens at 48 h (p < 0.01), whereas cortisol was higher in OC hens at week 2 (p < 0.05). No glucocorticoid differences were observed in drakes. A greater percentage of ducks in YC showed poorer gait at week -1 (p < 0.05) and also tended to be worse at weeks 2 and 3 (p = 0.07) compared to OC treatment. OC-fed hens showed higher egg production at week 1 (p < 0.05), heavier eggs at week -1 (p = 0.056), higher yolk weight at week -1 (p < 0.01), higher Haugh unit at weeks -2 and 3 (p = 0.06), and higher pigmented yolks at weeks -2, -1, 2, and 3 (p < 0.001) compared to YC treatment. Fertility was greater in the OC (p < 0.05) compared to YC treatment. These findings suggest that an OC diet may partially alleviate the physiological and reproductive effects of HS in breeder hens.