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High ambient temperatures compromise performance and productivity through reducing feed intake and decreasing nutrient utilization, growth rate, egg production, egg quality, and feed efficiency, which lead to economic losses in poultry. Environmental stress also leads to oxidative stress associated with a reduced antioxidant status in the bird in vivo, as reflected by increased oxidative damage and lowered plasma concentrations of antioxidant vitamins (e.g., vitamins E, A, and C) and minerals (e.g., Zn). Zinc has an important role in numerous biological processes in avian and mammalian species. For instance, Zn is an essential component of many enzymes, and it has both structural and catalytic functions in metalloenzymes. Furthermore, dietary Zn is required for normal immune function as well as proper skeletal development and maintenance. One of the most important functions of Zn is related to its antioxidant role and its participation in the antioxidant defense system. This work compiles past and present information about the role of Zn in heat-stressed poultry health.

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We evaluated the effects of vitamin C (L-ascorbic acid) and folic acid supplementation on performance, carcass characteristics and concentrations of the oxidative stress markers [malondialdehyde (MDA), homocysteine], adrenocorticotropic hormone (ACTH), vitamins C, E, A, B-12 and folic acid, and mineral status in broiler Japanese quail (Coturnix coturnix japonica) exposed to high ambient temperature (34 degrees C, 8 h/d, 0900-1700 h). The birds (n = 150; 10-d-old) kept at 34 degrees C were fed a basal diet (HS group) or the basal diet supplemented with 250 mg of L-ascorbic acid/kg of diet (Vit C group), 1 mg of folic acid/kg of diet (FA group) or both (Vit C + FA group), whereas birds kept at 22 degrees C were fed the basal diet (TN group). Supplementing heat-stressed quail with vitamin C and folic acid improved performance compared to the HS group. Effects generally were greatest in quail supplemented with both. Although supplementation did not consistently restore concentrations to those of the TN group, it increased serum concentrations of the vitamins under study. Furthermore, serum and tissue MDA, homocysteine and ACTH concentrations were lower in the supplemented groups than in the heat-stressed controls. Retention of N, ash, Ca, P, Zn, Fe, Cu and Cr were highest in the Vit C + FA group and lowest in the HS group (P < 0.05). The results of the study indicate that vitamin C and folic acid supplementation attenuates the decline in performance and antioxidant status caused by heat stress. Such supplementation may offer protection against heat stress-related depression in performance of Japanese quail.

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