This experiment was performed to evaluate the effect of vitamin C and methionine hydroxy analog (MHA) on performance, blood parameters, liver enzymes, activity of selected hormones, antioxidant activity of blood plasma, intestine morphology, and HSP70 gene expression in broilers under heat stress. Four hundred 1-day-old male chickens of commercial Ross 308 strain were used in a completely randomized design with 4 treatments and 5 replicates of 20 chickens each. The experimental treatments were as follows: (1) base diet based on maize soybean (the control), (2) base diet with 0.2% vitamin C, (3) base diet with 0.46, 0.36, and, 0.32% methionine hydroxy analog, in the starter, grower, and finisher periods, respectively, and (4) base diet with a mixture of 0.2% vitamin C and 0.46, 0.36, and 0.32% of methionine hydroxy analog in the starter, grower, and finisher periods respectively. Although numerically higher than control, the effect of the experimental diets on performance was not significant across the experimental period (P>0.05). Glucose and LDL concentrations under all experimental treatments were significantly reduced compared to the control (P<0.05). The concentrations of liver enzymes (AST and ALT) and antioxidant activity (SOD, GPx, and MDA) of broilers were significantly different from the control under combined MHA and vitamin C supplementation (P<0.05). All experimental diets led to significantly increased T4 concentrations, compared to control (P<0.05). The length and width of intestinal villi of broilers were significantly increased in all of the experimental treatments compared to the control (P<0.05). The difference in HSP70 gene expression was significantly reduced in all of the treatments compared to the control (P<0.05). The results of this experiment showed that the use of vitamin C and methionine hydroxy analog (MHA) can be effective in reducing the negative effects of heat stress.
Keywords: Antioxidant; Broiler; Heat stress; Methionine; Vitamin C.