Fig. 3.

In ovo supplementation improves performance at hatch and reduces antioxidant production when birds are exposed to heat stress during the rearing phase. In ovo manipulation during embryogenesis increased hatchability and had higher antioxidant enzyme activity and immune responses (Zhu et al., 2019). In ovo manipulated embryos when exposed to heat stress during the rearing phase showed lower antioxidant enzyme activity due to reduction in ROS generation in chickens (Slawinska et al., 2019). In parentheses are examples of in ovo injected materials. ROS = reactive oxygen species.