Gene expression in the skeletal muscle of broilers fed diets supplemented with vitamins C and E under acute or chronic heat stress

The objective of this study was to investigate if dietary supplementation with vitamins C and E, simultaneously, can neutralize, or reduce, the effects of acute and chronic heat stress on the expression of key genes in the skeletal muscle of chickens. A total of 384 one-day-old male broiler chickens were housed in thermoneutral chambers up to 28 days of age. They were then reallocated in groups of four per cage, in three environmentally controlled chambers: two thermoneutral (22.5 and 22.6 degrees C) and one for heat stress (32 degrees C). Half the chickens in each chamber were fed a diet supplemented with vitamins C (257 to 288 mg/kg) and E (93 to 109 mg/kg). In the thermoneutral chambers, half of the chickens were pair-fed to heat stressed chickens. Real-time quantitative PCR (RT-qPCR) was performed to access gene expression in breast muscle samples after 21 h (acute) or 16 days (chronic) under heat stress. Vitamin supplementation, under acute heat stress, contributed to downregulate avUCP, MSTN, and ACLY expressions. Vitamin supplementation reduced avUCP expression with pair-feeding compared to thermoneutral controls. Chickens did not show any changes in HSP70 expression level from both heat stress experiments, probably because they have adapted quickly. Under chronic heat stress, vitamin supplementation upregulated MSTN expression, possibly to reduce muscle mass hypertrophy and, consequently, maintain homeothermy. ACLY was not differentially expressed under chronic stress. In conclusion, exposing chickens to heat stress in the grower finishing phases impacted gene expression, but not all the effects were due to the high temperature per se. Diet supplementation with vitamins C and E under stress conditions (acute heat stress or feed restriction) produced the unexpected effect of decreasing avUCP expression, possibly a metabolic adaptation to regulate the antioxidative function. Diet supplementation with vitamins C and E may assist the body in coping with the effects of heat stress on metabolism by regulating the expression of MSTN and ACLY, genes involved in the maintenance of homeothermy.