Aditivos nutricionais para minimizar os efeitos do estresse por calor sobre a estabilidade oxidativa e a produção da carne de frangos de corte

Abstract

Three experiments were performed aiming to evaluate the antioxidant activity from an herbal compound and guanidine acetic acid - GAA supplementation in broiler diets. Experiment I: 1280 broiler chicks were distributed in a completely randomized design, in a 2x2 factorial scheme (control ration x ration with herbal compound vs thermoneutral x thermal stress environment). The zootechnical performance was determined weekly. At 42 days, the serum concentration of DPPH, MDA and carbonyl group, carcass yield, occurrence of myopathies and meat quality were evaluated. The results were submitted to analysis of variance through the statistical analysis software - SAS/STAT. Birds receiving diets with the herbal compound presented better Feed Convertion Ratio - FCR up to 35 days and lower concentration of the carbonyl group. Birds raised at high temperatures and receiving the herbal compound presented higher concentration of DPPH and less of MDA. The antioxidant resulted in increased deposition of muscle protein. It was concluded that the herbal compound was able to reduce lipid and protein oxidation, but did not present significant results on meat quality and performance. Experiment II: 1440 broiler chicks were distributed in a completely randomized design with 4 treatments and 9 replicates. (treatment 1: Control diet, treatment 2: Diet control with reduction of 50 Kcal, treatment 3: Diet control with reduction of 50 Kcal + 0.06% AGA, treatment 4: Diet control + 0.06% AGA). The commercial source of GAA used was CreAMINO®, with inclusion of 0.06%. The zootechnical performance was determined weekly. At 42 days, the serum concentration of uric acid, creatinine, lactate and glucose and of the enzymes CK, LDH, AST and GGT, carcass yield, occurrence of myopathies and meat quality were determined. The results were submitted to analysis of variance through SAS. Birds receiving the diet with energy reduction + GAA obtained better FC at 21 days. At 35 days, diets with GAA addition resulted in higher PV. Birds that received GAA presented lower percentage of abdominal fat. For the other variables there was no effect of treatments. It was concluded that GAA dietary supplementation improved feed conversion at 21 days, resulting in a greater weight gain at 35 days and a lower percentage of abdominal fat. Experiment III: 160 broilers were used from the experimental aviary. The birds were distributed in a completely randomized design in a 4 x 2 factorial scheme (diets x room temperature) (diets at room temperature, where the treatments were (treatment 1: Control diet + thermoneutral environment, treatment 2: Control diet with reduction of 50 Kcal + thermoneutral environment, treatment 3: Diet control with reduction of 50 Kcal + 0.06% GAA + Thermoneutral environment Treatment 4: Diet control + 0.06% GAA + Thermoneutral environment; Treatment 5: Control diet + acute heat stress; Treatment 6: Control diet with 50 Kcal reduction + acute heat stress treatment 7: Control diet with reduction of 50 Kcal + 0.06% GAA + heat stress treatment 8: Control diet + 0.06% AGA + acute heat stress. The variation of the weight gain before and after the acute heat stress was evaluated. At the end of the experimental period, the serum concentration of uric acid, creatinine, lactate and glucose and of the enzymes CK, LDH, AST and GGT and meat quality were determined. The results were submitted to analysis of variance through SAS/STAT. Birds that received a control diet or with GAA + energy reduction, when subjected to acute stress presented greater weight loss. In birds submitted to heat stress, a lower weight loss was observed in the diet with a reduction of 50 kcal or a reduction of 50 kcal + AGA. Birds raised under heat stress, consuming control presented higher initial pH. It was concluded that dietary supplementation of GAA did not improve the zootechnical performance, serum biochemistry and meat quality of broiler chickens submitted to acute heat stress.