Feed and Food Science and Nutrition Institute, Università Cattolica Sacro Cuore, 29122 Piacenza, Italy.
Department of Animal Science, Rasht Branch, Islamic Azad University, Rasht, Iran.
Poult Sci. 2017 Aug 1;96(8):2751-2760. doi: 10.3382/ps/pex086.
A study was conducted to evaluate growth performance, carcass traits, blood serum parameters, and immune responses of Ross 308 male broilers fed diets containing 2 different crude protein (CP) levels (97.5 and 100%) and 4 threonine (Thr) levels (100, 110, 120, and 130% of Ross recommendations for starter and grower periods). A completely randomized block design was adopted and main effects (CP and Thr) were arranged in a 2 × 4 factorial approach. Optimum growth performance was achieved when broiler requirements for CP and Thr were 100% satisfied. The 110% Thr inclusion in 97.5% CP diet increased ADG, ADFI, energy intake, and protein intake (Thr, P < 0.01; quadratic, P = 0.01). The G:F (linear, P = 0.05) and energy efficiency (linear, P = 0.04) tended to decreased (Thr, P = 0.09) by increasing Thr supplementation level, whereas protein efficiency tended to increase (CP, P = 0.06) by reducing CP level. The 110% Thr inclusion in 97.5% CP diet increased eviscerated carcass weight (CP × Thr, P = 0.03) and carcass yield (Thr, P = 0.08; quadratic, P = 0.05). The reduction of CP content promoted fat abdominal deposition (CP, P = 0.05). Incremental Thr raised abdominal fat (Thr, P = 0.01; linear, P = 0.01). The 97.5% CP diets resulted in higher serum concentrations of uric acid (CP, P = 0.02), total and high- and low-density lipoprotein-linked cholesterol (CP, P≤ 0.01), and alanine aminotransferase (CP, P = 0.05) and lower (CP, P = 0.01) concentrations of triglycerides and very low density lipoproteins compared with the 100% CP diets. However, the Thr inclusion improved serum lipid profile. Irrespective of CP content, incremental Thr levels up to 120% increased (Thr, P = 0.01) broiler immune responses against Newcastle disease virus and sheep red blood cells. In order to reduce dietary CP content, strategies to increase synthetic amino acid availability, such as the use of encapsulated amino acids, should be taken into account.
一项研究评估了两种不同粗蛋白（CP）水平（97.5%和 100%）和 4 种苏氨酸（Thr）水平（100%、110%、120%和 130%满足罗斯育雏和生长期推荐量）对罗斯 308 雄性肉鸡生长性能、胴体特性、血清参数和免疫反应的影响。采用完全随机分组设计，主效（CP 和 Thr）采用 2×4 因子设计。当肉鸡对 CP 和 Thr 的需求得到 100%满足时，可实现最佳生长性能。97.5%CP 日粮中添加 110%Thr 提高了 ADG、ADFI、能量摄入和蛋白质摄入（Thr，P＜0.01；二次，P=0.01）。随着 Thr 添加水平的增加，G:F（线性，P=0.05）和能量效率（线性，P=0.04）趋于下降（Thr，P=0.09），而蛋白质效率则趋于增加（CP，P=0.06）通过降低 CP 水平。97.5%CP 日粮中添加 110%Thr 提高了去内脏胴体重（CP×Thr，P=0.03）和胴体产率（Thr，P=0.08；二次，P=0.05）。CP 含量的降低促进了腹部脂肪沉积（CP，P=0.05）。增加 Thr 提高了腹部脂肪（Thr，P=0.01；线性，P=0.01）。97.5%CP 日粮导致尿酸（CP，P=0.02）、总胆固醇和高低密度脂蛋白结合胆固醇（CP，P≤0.01）、丙氨酸转氨酶（CP，P=0.05）血清浓度升高，而甘油三酯和极低密度脂蛋白（CP，P=0.01）血清浓度降低与 100%CP 日粮相比。然而，添加 Thr 改善了血清脂质谱。无论 CP 含量如何，添加高达 120%的 Thr 水平均可提高（Thr，P=0.01）对新城疫病毒和绵羊红细胞的肉鸡免疫反应。为了降低日粮 CP 含量，应考虑增加合成氨基酸可用性的策略，例如使用包被氨基酸。
