There has been extensive research on feeding broilers low-CP (LCP) diets to reduce nitrogen (N) excretion in the environment. It is well established that broilers fed LCP diets exhibit improvements in N efficiency, but this is coupled with inferior growth performance and poor carcass quality. Therefore, 2 experiments were undertaken to explore energy and N balance and performance in birds fed LCP diets to determine bird responses to dietary energy content. Both experiments used isoenergetic grower–finisher diets formulated to reduced- or high-CP (HCP) level. Measurements of AME, net energy, and N balance were conducted in a calorimetry system (experiment 1), and bird performance was measured in a floor pen feeding study (experiment 2). In experiment 1, birds fed the LCP diet had a comparatively higher ratio of energy (AME and net energy) intake to N retained, higher N efficiency (N retained/N intake), and higher ratio of energy retained as fat to total energy retention. In experiment 2, the LCP-fed birds had a comparatively higher feed conversion ratio at day 14 to 35 and a higher relative fat pad weight on day 35. Abdominal fat pad was positively correlated with the energy (AME and net energy) intake–to–weight gain ratio, suggesting that energy in excess was deposited as fat. These results present more highly efficient use of N in broilers reared on LCP diets. However, these birds also consumed excess energy relative to N retained, which was deposited as body fat accretion, thereby increasing the feed conversion ratio.

饲喂低CP（LCP）肉仔鸡以减少环境中氮（N）的排泄已经进行了广泛的研究。公认的是，饲喂LCP日粮的肉鸡表现出氮效率的提高，但这与生长性能差和car体质量差有关。因此，进行了2个实验，以探索饲喂LCP饲料的鸟类的能量，氮平衡和性能，以确定鸟类对膳食能量含量的反应。两项实验均采用了低能量或高CP（HCP）配方的等能量生长肥育日粮）级别。在热量测定系统（实验1）中测量AME，净能量和氮平衡（在实验2中进行），并在落地笔喂食研究中测量禽类的表现（实验2）。在实验1中，饲喂LCP日粮的鸡的能量（AME和净能量）摄入量与保留的氮的比例相对较高，氮的利用率（保留的氮/氮的摄入量）较高，以脂肪形式保留的能量与总能量保留量的比例较高。在实验2中，LCP饲喂的家禽在第14天到第35天的饲料转化率相对较高，在第35天的相对脂肪垫重量较高。腹部脂肪垫与摄入的能量（AME和净能量）呈正相关–体重增加比率，表明多余的能量以脂肪的形式沉积。这些结果表明，在LCP日粮饲养的肉鸡中，氮的使用效率更高。然而，