The magnitude and timing of broiler responses to dietary amino acid (AA) density can vary between sexes and among genetic lines. Two experiments (Exp) were conducted to determine the responsiveness of Cobb MV × 700 broilers to changes in dietary AA density. In Exp 1, low (L), medium (M), and high (H) AA density diets were maintained across starter and grower phases in a 28 d growth performance trial (all males). In Exp 2, combinations of L, M, and H-AA density diets were varied across 4 feeding phases to evaluate the effect of 6 AA feeding regimens (HHHH, HHHM, HHMM, HMMM, MMMM, and HHLL) on growth performance, carcass composition, and breast muscle myopathies of broilers reared sex-separately. Body weight gain, feed intake (FI), and FCR responded positively to increased AA density during the starter and grower phases (0 to 28 d) of Exp 1. In Exp 2, broiler responses to AA density from 0 to 28 d diminished by the conclusion of the finisher phase (day 35), and FCR was the only measurement influenced by dietary AA density through day 46. Carcass characteristics and breast muscle myopathies were unaffected by AA density, with the exception of fat pad percentage, which decreased with increasing AA density. These data indicate that Cobb MV × 700 broilers may be less responsive to dietary AA density than other high-yielding broiler strains and further research to establish digestible AA:Lys ratios or dietary energy concentrations that optimize responses to increased AA density are warranted.

肉鸡对日粮氨基酸（AA）密度的反应的大小和时间可能会因性别和遗传系而异。进行了两个实验（实验）来确定Cobb MV×700肉鸡对日粮AA密度变化的响应性。在实验1中，在28天的生长性能试验（所有雄性）中，在起始阶段和生长阶段保持低（L），中（M）和高（H）AA密度饮食。在实验2中，L，M和H-AA密度日粮的组合在4个喂养阶段中进行了变化，以评估6种AA喂养方案（HHHH，HHHM，HHMM，HMMM，MMMM和HHLL）对生长性能，car体的影响肉鸡的组成和胸肌肌病。在实验1的起始阶段和生长阶段（0至28 d），体重增加，摄食量（FI）和FCR对AA密度增加产生了积极的响应。在实验2中，肥育阶段结束（第35天）后，肉鸡对0至28 d AA密度的反应减弱，而FCR是直至46天受饮食AA密度影响的唯一测量指标。Car体特征和胸肌肌病不受影响脂肪密度的增加，AA密度降低。这些数据表明，Cobb MV×700肉鸡可能比其他高产肉鸡菌株对日粮AA密度的响应低，因此有必要进行进一步研究以建立可消化的AA：Lys比或日粮能量浓度，以优化对AA密度增加的响应。A体密度和胸肌肌病不受AA密度的影响，脂肪垫百分比除外，后者随AA密度的增加而降低。这些数据表明，Cobb MV×700肉鸡可能比其他高产肉鸡菌株对日粮AA密度的响应低，因此有必要进行进一步研究以建立可消化的AA：Lys比或日粮能量浓度，以优化对AA密度增加的响应。A体密度和胸肌肌病不受AA密度的影响，脂肪垫百分比除外，后者随AA密度的增加而降低。这些数据表明，Cobb MV×700肉鸡可能比其他高产肉鸡菌株对日粮AA密度的响应低，因此有必要进行进一步研究以建立可消化的AA：Lys比或日粮能量浓度，以优化对AA密度增加的响应。