Peroxidação lipídica, desempenho e características de carcaça de frangos de corte estressados pelo calor e suplementados com zinco e selênio

Abstract

CHAPTER II: The objective of this study was to 28 evaluate the effects of the cyclic thermal stress and supplementation of zinc and selenium on 29 the diet of male broiler chickens on the cloacal temperature (CT) and the blood levels of 30 thiobarbituric acid reactive substances (TBARS). 1 day old chicks (N = 2.400) were allocated 31 in 80 boxes (30 chicks per box) and raised at the natural environmental temperature until the 32 14th day, when half of them was submitted to cyclic heat stress (from 7 am to 7 pm). CT was 33 weekly checked in 2 broilers per box, according to a randomized design with a 2x5 factorial [2 environments: control (C) and heat stress (EC), and 5 levels 34 of supplementation: S1) 35 control ration (premix commercial mineral); S2) 40 ppm of inorganic Zn; S3) 40 ppm of 36 organic Zn; S4) 40 ppm of inorganic Zn e 0.2 ppm of organic Se; and S5) 40 ppm of organic 37 Zn and 0.2 ppm of organic Se]. For the variable TBARS determination (1 broiler per box) in 2 38 periods of blood collect (21 e 42 days). Data were submitted to variance analysis and the 39 means were compared by Tukey test (5%). The blood concentrations of TBARS were not 40 affected by changes in the ambient temperature, diet supplementation and broiler age or by 41 the interaction among these factors. At the 35th and 42nd day, broilers submitted to the cyclic 42 heat stress presented elevation in the cloacal temperature. Thus, the broiler chickens 43 submitted to cyclic heat stress and supplemented with zinc and selenium had no reduction in 44 the lipid peroxidation, but they presented increase in the cloacal temperature. 45 KEY WORDS: broiler, minerals, oxidative stability, environmental, body temperature. CHAPTER III: This study aimed to determinate the effect of heat stress on the performance and carcass characteristics of broiler chickens supplemented with zinc and selenium. 2400 male broiler chickens were housed in a shed with 80 boxes, in a entirely randomized design, factorial 2x5, being 2 environments [control (C) and heat stress (EC)] and 5 supplementation levels [S1) control ration (Premix mineral commercial); S2) control ration with 40 ppm of inorganic Zn; S3) control ration with 40 ppm of organic Zn; S4) control ration with 40 ppm of inorganic Zn and 0.2 ppm of organic selenium; and S5) control ration with 40 ppm of organic Zn and 0.2 ppm of organic selenium], in a total of 10 treatments with 8 replications of 30 broilers each. It was evaluated: weight gain, feed consumption, feed conversion, viability, body weight, and yield of carcass and parts (breast with bones, breast without bones, thighs and wings). Data were submitted to ANOVA and compared by Tukey test (5%). Weight gain and feed conversion were negatively influenced by the heat stress. There was interaction between ambient and supplement levels for the carcass characteristics, however neither the ambient nor the supplement levels changed the yield of breast with bones, breast without bones, thighs and wings. The carcass characteristics more affected by the studied variables were the body weight and the eviscerated carcass. Thus, cyclic elevations in the ambient temperature worsen the industrial performance of broiler chickens, but not their viability, which was improved. Zinc and selenium supplementation not improve the performance and the carcass characteristics of broiler chicken independently of the thermal condition of the ambient.