Faculty of Animal Husbandry, University of Jambi, Jambi 36361, Indonesia.
Department of Animal Science, The Pennsylvania State University, University Park, PA 16802.
Poult Sci. 2019 Sep 1;98(9):3818-3827. doi: 10.3382/ps/pez091.
This study evaluated reduced dietary CP and supplementing amino acid analogs to sustain growth and carcass weight in 0- to 21-day-old Cobb × Avian-48 male broiler chicks. A total of 6 diets with 3 levels of CP (22.5, 19.5, and 16.5%) and 2 sources of AA analogs, either synthetic amino acids (SA) or keto-/hydroxy-acids (KA), were assigned randomly to 36 cages (8 chicks/cage) in a 3 × 2 factorial design. For SA diets, DL-Met, DL-Met + L-Ile, and D-Met + L-Ile + L-Val were used to supplement 22.5, 19.5, and 16.5% CP diets, respectively, and for corresponding KA diets, DL-Met was replaced with methionine hydroxy analog (MHA), L-Ile was replaced with keto-Ile, and L-Val was replaced with keto-Val. Water and all isocaloric diets (3,050 kcal ME/kg) were given ad libitum. Lowering dietary CP to 16.5% reduced BW at 7, 14, and 21 D (P ≤ 0.0001) and feed intake at 8 to 14, 15 to 21, and 0 to 21 D (P ≤ 0.001). Body weight gain (BWG) was reduced and feed-to-gain ratio (FGR) was increased (P ≤ 0.003 to 0.0001) at all times for chicks fed 16.5% CP; however, chicks fed 22.5 and 19.5% CP had comparable performance. Differences in 0 to 7 D BWG (SA, 122.9 vs. KA, 113.9 g/bird; P ≤ 0.04), a 0 to 21 D FGR cumulative effect (1.45 vs. 1.51; P ≤ 0.02), and a 15 to 21 D (P ≤ 0.04) and 0 to 21 D (P ≤ 0.05) CP × AA interaction were also observed. Greater liver weight among 16.5 vs. 19.5 or 22.5% CP fed chicks was found at 14 and 21 D (P ≤ 0.0001 and P = 0.06, respectively). Lower dietary CP reduced spleen weight on day 21 birds (P ≤ 0.0005) with lighter spleens among 16.5 and 19.5% vs. the 22.5% CP fed group (0.090, 0.095, 0.119 g/100 g BW, respectively). Breast weight at 21 D was significantly less for 16.5 vs. 22.5% CP fed chicks. Fat pad weight on day 21 was heaviest among 16.5% chicks (P ≤ 0.0004). Overall, lowering dietary CP to 16.5% had a negative effect, but keto-acid supplementation supported 0 to 21 D broiler growth compared to SA; however, transamination efficiency of KA may be lower for 0 to 7D old chicks compared to older birds.
本研究评估了降低饲粮 CP 水平并用氨基酸类似物补充来维持 0-21 日龄科宝 × 爱拔益加雄性肉鸡的生长和胴体体重。在一个 3×2 因子设计中，将 6 种饲粮（3 个 CP 水平（22.5、19.5 和 16.5%）和 2 种 AA 类似物来源，即合成氨基酸（SA）或酮/羟氨基酸（KA））随机分配给 36 个笼位（每笼 8 只鸡）。对于 SA 饲粮，分别用 DL-Met、DL-Met+L-Ile 和 D-Met+L-Ile+L-Val 来补充 22.5、19.5 和 16.5%CP 饲粮，而相应的 KA 饲粮中，用甲硫氨酸羟类似物（MHA）替代 DL-Met，用酮异亮氨酸替代 L-Ile，用酮缬氨酸替代 L-Val。自由饮水和所有等能饲粮（3050 千卡 ME/kg）。降低饲粮 CP 水平至 16.5%会降低 7、14 和 21 日龄时的 BW（P≤0.0001）和 8-14、15-21 和 0-21 日龄时的采食量（P≤0.001）。所有时间内，16.5% CP 组的雏鸡 BWG 降低，FGR 增加（P≤0.003 至 0.0001）；然而，饲喂 22.5 和 19.5% CP 的雏鸡具有相似的性能。0-7 日龄 BWG 的差异（SA，122.9 vs. KA，113.9 g/只；P≤0.04）、0-21 日龄 FGR 累积效应（1.45 vs. 1.51；P≤0.02）以及 15-21 日龄（P≤0.04）和 0-21 日龄（P≤0.05）CP×AA 互作也观察到了。在 14 和 21 日龄时，与 19.5 或 22.5% CP 相比，16.5% CP 组的雏鸡肝脏重量更高（P≤0.0001 和 P=0.06）。降低饲粮 CP 水平会降低 21 日龄雏鸡的脾脏重量（P≤0.0005），与 16.5% 和 19.5% CP 组相比，16.5% CP 组的脾脏更轻（0.090、0.095、0.119 g/100 g BW，分别）。21 日龄时，16.5% CP 组的胸肌重量显著低于 22.5% CP 组。21 日龄时，腹脂垫重量在 16.5% CP 组最重（P≤0.0004）。总的来说，将饲粮 CP 水平降低至 16.5% 会产生负面影响，但与 SA 相比，KA 补充剂支持 0-21 日龄肉鸡的生长；然而，与年长的鸡相比，KA 的转氨效率可能对 0-7 日龄的雏鸡较低。
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