Two broiler lines A and B were fed experimental diets from 21 to 42 days with an objective to determine Pectoralis major protein turnover (PT) as affected by the dietary amino acid (AA) levels and ambient temperature. Experimental diets (n = 9 replicate pens per diet) were formulated to 3,150 kcal/kg with five levels of digestible lysine (dLys) −80, 90, 100, 110 and 120% of recommended AA level giving g dlys/Mcal values of 2.53, 2.85, 3.17, 3.48 and 3.80 respectively. All other AA was formulated to a fixed ratio to dLys. Fractional synthesis or degradation rates (FSR or FDR) of P. major were measured on day 36 and day 42 for all dietary treatment levels for both broiler lines using stable isotope of AA (¹⁵N‐phenylalanine) as metabolic tracer. Experimental feeding studies were conducted once in hot season (24‐hr mean ~ 85.3°F; 80.9% RH) and repeated in cool season (24‐hr mean ~ 71.6°F; 61.7% RH) of the year. The FSR values increased (p < .05) as digestible AA in diet increased for both broiler lines in hot season until break point FSR occurring at 106.2% AA level. The average FSR values measured were higher for Line B at day 36 (20.98%/D for Line B vs. 20.69%/D for Line A) and at day 42 (16.07%/D for Line B vs. 12.47% D for Line A). FDR values observed at day 36 and day 42 were not different between lines (p > .05). Similar trends but elevated values of FSR and FDR in cool season than in hot season were recorded for both the lines. Line B showed the higher mixed muscle protein accretion (%/D) than Line A by actually increasing the FSR which was correlated by higher lean mass deposition and higher feed intake (p < .05). The overall findings indicated that PT response in P. major due to effects of digestible AA levels and ambient temperature was different and line‐specific.

中文翻译：

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日粮氨基酸水平和环境温度对两个肉鸡品系肥育期胸大肌混合肌蛋白更新的影响。

在21至42天的实验日粮中给两个肉鸡A和B饲喂了实验性日粮，目的是确定受饮食氨基酸（AA）水平和环境温度影响的胸大肌主要蛋白质周转率（PT）。实验饮食（Ñ 每饮食= 9复制笔）配制到3150千卡/ kg的可消化赖氨酸（的D-Lys）-80，90，100，110和推荐的AA水平的120％得到的五个级别克2.53的D-Lys / 1000千卡值，2.85、3.17、3.48和3.80。所有其他AA均以相对于dLys的固定比例配制。分数合成或降解速率的（FSR或FDR）P.主要第36天和42天测量被用于使用AA的稳定同位素都肉鸡线的所有的饮食治疗水平（¹⁵N-苯丙氨酸）作为代谢示踪剂。在一年中的炎热季节（24小时平均〜85.3°F；相对湿度80.9％）进行一次实验性喂养研究，并在凉爽季节（24小时平均〜71.6°F； 61.7％RH）重复进行饲喂研究。 在炎热季节，由于两种肉鸡品系的日粮中可消化的AA增加，FSR值增加（p <.05），直到断点FSR出现在106.2％AA水平。在第36天，B行的平均FSR值较高（B行为20.98％/ D，A行为20.69％/ D），第42天（B行为16.07％/ D，B行为12.47％D）更高一种）。各行之间第36天和第42天观察到的FDR值没有差异（p > .05）。这两条线都记录了相似的趋势，但凉季的FSR和FDR值高于炎热季节。B线通过实际增加FSR而显示出比A线更高的混合肌蛋白积累（％/ D），这与较高的瘦肉沉积和较高的采食量相关（p  <.05）。总体研究结果表明，由于可消化的AA水平和环境温度的影响，大果疟原虫的PT响应是不同的，并且是特定的。