Expressão gênica, produção de ros e atividade enzimática em função de suplementação de metionina e estresse térmico em aves

• Autor(a) principal: Del Vesco, Ana Paula
• Data de Publicação: 2012
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Estadual de Maringá (RI-UEM)
• Texto Completo: http://repositorio.uem.br:8080/jspui/handle/1/1744
• topic: Frango de corte; Metionina; Genes mitocondriais; RNA; Codorna; Estresse oxidativo; Estresse térmico; Brasil.; Broiler; Methionine; Mitochondrial genes; RNA; Quail; Oxidative stress; Heat stress; Brazil.; Ciências Agrárias; Zootecnia

The growth rate of birds occurs due to the feed efficiency and deposition of muscle mass, as well as environmental conditions. Thus, this study aimed to evaluate the weight gain and feed conversion and the expression of mitochondrial genes involved in the energy synthesis, mRNA UCP (uncoupling protein), mRNA ANT (adenine nucleotide translocator) and mRNA COXIII (cytochrome c oxidase subunit III), and the expression of genes involved in animal growth, GHR mRNA (growth hormone receptor) and IGF-I (insulin-like growth factor I) in the liver and in the breast muscle of broilers fed with diets containing two sources and two levels of methionine supplementation, and to evaluate the influence of acute thermal stress on the production of mitochondrial ROS and glutathione peroxidase activity in the liver of quails. In this work broilers from 22 to 42 days of age were distributed into five treatments (basal diet, supplementations of first level of DL-methionine, of second level of DL-methionine, of first level of MHA-FA and second level of MHA-FA). At the end of the experimental period the birds were killed by cervical dislocation, the breast muscle and the liver were collected for total RNA extraction. The cDNA was amplified using specific primers designed for the genes analyzed by qRT-PCR. The birds fed with second level of methionine supplementation were more efficient in the feed conversion, regardless the commercial source used. The best weight gain was observed in the second level of DLmethionine supplementation. Significant lower amount of mRNA UCP was observed in the breast muscle of animals fed with diets containing added methionine, being the highest expression of this gene observed in broilers fed with the basal diet, treatment which was also responsible for the worst feed efficiency. The mRNA UCP expression in the liver, and the mRNA COX III and mRNA ANT expression in the liver and in the muscle was not influenced by methionine supplementation. The GHR and IGF-I gene expression in the breast muscle was not affected by methionine supplementation. However, a significant difference between the basal diet and the second level of DLmethionine on GHR mRNA expression in the liver was observed, whereas animals which received this level of supplementation showed higher expression of the gene. The expression of IGF-I in the liver was higher in the animals fed with diets supplemented with methionine compared to those fed with basal diet. The second level of DLmethionine supplementation also had the highest expression in relation to those animals which received the first level of DL-methionine supplementation (1.56 AU vs 0.97 AU).The methionine supplementation improved weight gain and feed efficiency, as expected, in part, by influencing the expression of genes involved in these characteristics. The birds? performance is also affected by environmental conditions. Thus, an experiment was conducted with the purpose of evaluating the production of mitochondrial ROS and glutathione peroxidase activity. Quails with 30 days of age were divided into two groups, the animals pertaining to thermoneutral treatment were slaughtered immediately and the second group was subjected to thermal stress of 34oC for 24 hours. To analyze the production of ROS, the livers were collected for the isolation of mitochondria and subsequent analysis of mitochondrial ROS. Glutathione peroxidase activity was determined using hydrogen peroxide (H2O2), and based on the amount of NADPH oxidized. A higher production of mitochondrial ROS was observed in animals subjected to thermal stress, 0.34 vs 0.22, for reactions containing only rotenone, and 0.31 vs 0.23, in reactions containing rotenone and antimycin. Quails that remained in the environment of heat stress also had significantly higher glutathione peroxidase activity in the hepatocytes (47.8 vs. 39.6). Therefore, it was observed that acute thermal stress of 34oC for a period of 24 hours was able to act in the mitochondrial ROS production and in the glutathione peroxidase activity in the liver of quails.