Consequences of heat stress on broilers experimentally challenged with eimeria maxima oocysts and treated with monensin or nicarbazin

Heat stress has been shown to both reduce Eimeria acervulina oocyst output and to cause nicarbazin-induced heat stress (HS) toxicity. Here, we examined the effect constant chronic HS has on Eimeria maxima oocyst production. It was concluded that in broilers subjected to constant chronic HS, the production of E. maxima oocysts is significantly reduced. mRNA expression experiments suggest that exposing nicarbazin-fed broilers to constant chronic HS likely leads to oxidative stress. This may induce a protective response by suppressing appetite, increasing antioxidant capacity, increasing protection against hepatic lipogenesis, inhibiting ROS production and inhibiting intestinal motility. This may explain why HS-acclimated broilers are less susceptible to nicarbazin-induced HS toxicity when compared non-acclimated birds. Furthermore, mRNA expression results also suggest that constant chronic HS improves antioxidant capacity, reduces ROS production, and reduces motility of parasitized epithelial cells. These changes may influence E maxima multiplication, reducing Eimeria oocyst output.