Parental intake of high-carotenoid orange corn diet alleviated glucocorticoid and fear response but not growth in F1 Pekin ducks

Prolonged heat stress (HS) in poultry has both immediate and transgenerational effects. Carotenoids, with their antioxidant properties, may enhance stress tolerance by reducing oxidative damage. This study assessed the effects of parental HS on offspring (F1) and whether feeding high-carotenoid orange corn (OC) to breeders mitigates these effects. Breeder Pekin ducks were fed either OC or yellow corn (YC) for 3 weeks before and during a 3-week HS exposure. A control breeder group (CON) was kept under thermoneutral conditions with a YC diet. Eggs collected in the final 3 days of HS. CON eggs were collected during the same days and incubated in the same incubator as OC and YC groups. Resulting offspring was allocated to treatment based on parental treatment (n = 56/group: OCF1, YCF1, CONF1) and reared to 5 weeks of age. Weekly body weight (n = 20/group), body condition scores (n = 20 ducks/treatment), and novel object test were measured. At week 3, ducks (n = 8/injection type/group) received Adrenocorticotropic hormone (ACTH; 0.0625 mg/kg) or saline, and blood was collected at 0, 1, 2, 3, and 4 h post-injection for glucocorticoid and heterophil-to-lymphocyte ratio (HLR) analysis. Corticosterone increased at 1 h in all ACTH-injected groups (p < 0.001) and remained elevated in YCF1 at 2 h compared to the CONF1 and OCF1 treatments. Baseline cortisol was higher in F1 from HS parents than CONF1 (p < 0.01) and remained elevated at 1 and 4 h post-ACTH (p < 0.05). HLR at 3 h was higher in YCF1-ACTH compared to CONF1-ACTH (p < 0.05). Body weight was higher in CONF1 compared to OCF1 and YCF1 at weeks 2 - 5 (p < 0.05). Fearful behavior was higher in YCF1 at weeks 1 (p < 0.01), 2 (p < 0.01), and 4 (p = 0.09) compared to CONF1. In conclusion, while parental HS reduced growth in F1 ducks, OC-fed breeders produced offspring without the exaggerated physiological responses to stress. These observations suggest a transgenerational effect of parental OC diet on stress-related physiological responses in the offspring.