Rosebrough R, McMurtry J, Steele N
USDA-Agricultural Research Service, Beltsville Agricultural Research Center, MD 20705.
Growth. 1987 Autumn;51(3):309-20.
Both a decrease in the dietary carbohydrate level and an increase in the protein level decrease lipogenesis in chicks. Interpreting results of previous experiments can be confounded by alterations in the quantity of carbohydrate because as protein was added to the diets used in these studies, carbohydrate was decreased. In the present study, diets containing 13, 16, 19 or 23% protein and 70% carbohydrate calories were fed to Ross male chicks from 1 to 4 weeks of age to determine the effect of dietary protein level (% crude protein) on growth and intermediary metabolism in 2, 3, and 4-wk old chicks. All treatment groups were limited to that amount of feed consumed by the 23% protein group. There were no significant differences in body weights among the treatment groups at 4 wk of age. An increase in dietary protein (23 vs. 13%) increased (P less than 0.05) in vitro glucose production by liver slices from 4-wk old chicks. In contrast, the same increase in dietary protein decreased (P less than 0.05) in vitro lipogenesis by liver slices from 2, 3, and 4-wk old chicks. The same increase in dietary protein increased (P less than 0.05) both insulin (INS) and thyroxine (T4) and decreased (P less than 0.05) triiodothyronine (T3). Serum T3 and T4 concentrations were less (P less than 0.05) and INS concentrations were greater (P less than 0.05) in 4-wk old chicks compared to 2-wk old chicks.
日粮碳水化合物水平的降低和蛋白质水平的升高均会降低雏鸡的脂肪生成。由于在这些研究中使用的日粮添加蛋白质时碳水化合物会减少，所以碳水化合物量的改变可能会混淆先前实验的结果。在本研究中，给1至4周龄的罗斯雄性雏鸡饲喂蛋白质含量为13%、16%、19%或23%且碳水化合物热量为70%的日粮，以确定日粮蛋白质水平（%粗蛋白）对2、3和4周龄雏鸡生长及中间代谢的影响。所有处理组的采食量均限制为23%蛋白质组的采食量。4周龄时，各处理组的体重无显著差异。日粮蛋白质增加（23%对13%）会使4周龄雏鸡肝脏切片的体外葡萄糖生成增加（P<0.05）。相反，相同的日粮蛋白质增加量会使2、3和4周龄雏鸡肝脏切片的体外脂肪生成减少（P<0.05）。相同的日粮蛋白质增加量会使胰岛素（INS）和甲状腺素（T4）增加（P<0.05），并使三碘甲状腺原氨酸（T3）减少（P<0.05）。与2周龄雏鸡相比，4周龄雏鸡的血清T3和T4浓度较低（P<0.05），INS浓度较高（P<0.05）。
