PDF(Pubmed)
Abstract：
This research compared how different levels of dietary crude protein (CP) and apparent metabolizable energy (AME) affect the growth performance, nitrogen utilization, serum parameters, protein synthesis, and amino acid (AA) metabolism in broilers aged 1 to 10 days. In a 4 × 3 factorial experimental design, the broilers were fed four levels of dietary CP (20%, 21%, 22%, and 23%) and three levels of dietary AME (2800 kcal/kg, 2900 kcal/kg, and 3000 kcal/kg). A total of 936 one-day-old male Arbor Acres broilers were randomly allocated to 12 treatments with 6 replications each. Growth performance, nitrogen utilization, serum parameter, gene expression of protein synthesis, and AA metabolism were evaluated at 10 d. The results revealed no interaction between dietary CP and AME levels on growth performance (p > 0.05). However, 22% and 23% CP enhanced body weight gain (BWG), the feed conversion ratio (FCR), total CP intake, and body protein deposition but had a detrimental effect on the protein efficiency ratio (PER) compared to 20% or 21% CP (p < 0.05). Broilers fed diets with 2800 kcal/kg AME showed increased feed intake (FI) and inferior PER (p < 0.05). Broilers fed diets with 3000 kcal/kg AME showed decreased muscle mRNA expression of mammalian target of the rapamycin (mTOR) and Atrogin-1 compared to those fed diets with 2800 kcal/kg and 2900 kcal/kg AME (p < 0.05). Increasing dietary CP level from 20% to 23% decreased muscle mTOR and increased S6K1 mRNA expression, respectively (p < 0.05). The muscle mRNA expression of Atrogin-1 was highest for broilers fed 23% CP diets (p < 0.05). The mRNA expression of betaine homocysteine methyltransferase (BHMT) and Liver alanine aminotransferase of the 22% and 23% CP groups were higher than those of 20% CP (p < 0.05). Significant interactions between dietary CP and AME levels were observed for muscle AMPK and liver lysine-ketoglutarate reductase (LKR) and branched-chain alpha-keto acid dehydrogenase (BCKDH) mRNA expression (p < 0.05). Dietary AME level had no effect on muscle AMPK mRNA expression for broilers fed 21% and 22% CP diets (p > 0.05), whereas increasing dietary AME levels decreased AMPK mRNA expression for broilers fed 23% CP diets (p < 0.05). The mRNA expression of LKR and BCKDH was highest for broilers fed the diet with 2800 kcal/kg AME and 22% CP, while it was lowest for broilers fed the diet with 3000 kcal/kg AME and 20% CP. The findings suggest that inadequate energy density hindered AA utilization for protein synthesis, leading to increased AA catabolism for broilers aged 1 to 10 days, and a dietary CP level of 22% and an AME level of 2900 to 3000 kcal/kg may be recommended based on performance and dietary protein utilization.
摘要：
本研究比较了不同水平饲粮粗蛋白(CP)和表观代谢能(AME)对生长性能的影响,氮利用，血清参数，蛋白质合成，1~10日龄肉仔鸡的氨基酸(AA)代谢。在4×3阶乘实验设计中，饲喂肉鸡四个水平的日粮CP(20%，21%,22%,和23%)和三个水平的日粮AME(2800千卡/千克，2900kcal/kg,和3000千卡/千克）。将936只1日龄雄性ArborAcres肉鸡随机分配到12个处理中，每个处理6个重复。增长业绩，氮利用，血清参数,蛋白质合成的基因表达，在10d时评估AA代谢。结果表明，饲粮CP和AME水平对生长性能没有交互作用（p>0.05）。然而,22%和23%CP增加了体重（BWG），饲料转化率(FCR)，总CP摄入量，和身体蛋白质沉积，但与20％或21％CP相比，对蛋白质效率比（PER）具有不利影响（p<0.05）。饲喂具有2800kcal/kgAME的日粮的肉鸡显示出增加的采食量(FI)和较差的PER(p<0.05)。与饲喂2800kcal/kg和2900kcal/kgAME的饲粮相比，饲喂3000kcal/kgAME的饲粮的肉鸡显示哺乳动物雷帕霉素靶蛋白（mTOR）和Atrogin-1的肌肉mRNA表达降低（p<0.05）。将日粮CP水平从20%增加到23%降低肌肉mTOR并增加S6K1mRNA表达,分别为(p<0.05)。饲喂23%CP日粮的肉鸡的Atrogin-1的肌肉mRNA表达最高(p<0.05)。22％和23％CP组甜菜碱同型半胱氨酸甲基转移酶（BHMT）和肝丙氨酸氨基转移酶的mRNA表达均高于20％CP组（p<0.05）。饮食CP和AME水平之间观察到肌肉AMPK和肝脏赖氨酸-酮戊二酸还原酶（LKR）和支链α-酮酸脱氢酶（BCKDH）mRNA表达的显着相互作用（p<0.05）。饲粮AME水平对饲喂21％和22％CP日粮的肉仔鸡肌肉AMPKmRNA表达没有影响（p>0.05）。而增加日粮AME水平降低了饲喂23％CP日粮的肉仔鸡的AMPKmRNA表达（p<0.05）。LKR和BCKDH的mRNA表达在饲喂2800kcal/kgAME和22％CP的肉仔鸡中最高。而饲喂3000kcal/kgAME和20％CP的肉鸡最低。研究结果表明，能量密度不足阻碍了AA对蛋白质合成的利用，导致1至10日龄肉鸡AA分解代谢增加，根据性能和饮食蛋白质利用率，建议饮食CP水平为22％，AME水平为2900至3000kcal/kg。
