Skeletal Muscle Growth of Broiler Chicken

为了研究环境温度对肉仔鸡生产性能、血浆激素水平和骨骼肌蛋白质周转率的影响，本试验共进行了4个试验：试验1测定了高（34 ℃）和低（19 ℃）环境温度下肉仔鸡的生产性能和骨骼肌蛋白质合成与分解速率。尽管这些鸟被强制喂食，但在中等环境（25 ℃）中的表现（包括肌肉生长）上级高温和低温环境。然而，肌肉蛋白质的合成和分解的速率在热环境中显着降低。实验2研究了甲状腺功能在热环境下降低肌肉蛋白质周转中的作用。蛋白质合成和分解的速率在热环境中降低，甲状腺素给药使蛋白质合成和分解的速率降低正常化。实验3和实验4旨在阐明环境温度对肌肉蛋白质周转、产热以及血浆甲状腺素和皮质酮浓度的影响。蛋白质合成和分解率和产热率在较温暖的环境中较低，正如预期的那样，血浆甲状腺素和皮质酮也较低。这表明，皮质酮以及甲状腺激素可能在降低热环境时的产热和蛋白质周转中起重要作用，提示热致生长迟缓的机制。

Four experiments were conducted to clarify the effect of environmental temperature on the performance, plasma hormones concentrations and skeletal muscle protein turnover rate in force-fed broiler chicken.In experiment 1, the performance and rates of skeletal muscle protein synthesis and breakdown of chickens were measured under high (34ﾟC) and low (19ﾟC) environmental temperatures. The performance including muscle growth was superior in the moderate environment (25ﾟC) than in the hot and the cool environments despite the birds were force-fed. However, both the rates of muscle protein synthesis and breakdown were significantly lower in the hot environment. Inexperiment 2, the role of thyroid function in decreasing muscle protein turnover under hot environment was examined. The rates of protein synthesis and breakdown were decreased in the hot environment and the decreased rates of protein synthesis and breakdown were normalized by thyroxine administration. Experiment 3 and 4 were conducted to clarify the effect of ambient temperature on muscle protein turnover, heat production and plasma concentrations of thyroxine and corticosterone. The rates of protein synthesis and breakdown and heat production were lower in the warmer environment as was expected and both plasma thyroxine and corticosterone were also lower in the warmer environment. This indicates that corticosterone as well as thyroid hormone may play important roles in decreasing heat production and protein turnover when exposed to hot environment, suggesting a mechanism of the growth retardation due to heat.