Rosebrough R W, Mitchell A D, McMurtry J P
Livestock and Poultry Science Institute, United States Department of Agriculture-Agricultural Research Service, Beltsville Agricultural Research Center, MD 20705, USA.
J Nutr. 1996 Nov;126(11):2888-98. doi: 10.1093/jn/126.11.2888.
Although changes in dietary crude protein levels change metabolism in broiler chickens, there is little information concerning the time course of the process of adaptation. Therefore, male Indian River broiler chickens were fed diets containing either 120 or 210 g protein/kg from 7 to 28 d of age and then were fed the other level for an additional 12 d. Birds were bled and killed at 0, 2, 5, 7, 9 and 12 d following the reversals. Measurements taken at these intervals included in vitro lipogenesis, growth and feed consumption, hepatic enzyme activities and plasma metabolites and metabolites. Birds fed the lower level of crude protein were smaller and less efficient in growth from 7 to 28 d. Feeding these birds a higher protein diet from 28 to 40 d improved both growth and feed efficiency. Lipogenesis was also greater and plasma insulin-like growth factor-I (IGF-I) less in birds fed the lower protein diet. Switching dietary treatments increased and decreased lipogenesis as birds were switched from high to low protein and from low to high protein diets, respectively. Half-maximal changes were observed 4 d after the reversal and maximal changes 7 d after the reversal. In contrast, switching dietary treatments decreased and increased plasma IGF-I as birds were switched from high to low protein and from low to high protein diets, respectively. Half-maximal changes were observed 2 d after the reversal. Of the three hepatic enzymes monitored, malic enzyme activity most closely followed the rapid changes in in vitro lipogenesis. Plasma IGF-I may be a more sensitive indicator of changes in dietary protein than changes in intermediary metabolisms.
虽然日粮粗蛋白水平的变化会改变肉鸡的新陈代谢，但关于适应过程的时间进程的信息却很少。因此，雄性印第安河肉鸡在7至28日龄时饲喂含120或210克蛋白质/千克的日粮，然后再饲喂另一种水平的日粮12天。在日粮转换后的0、2、5、7、9和12天对鸡进行采血和宰杀。在这些时间间隔进行的测量包括体外脂肪生成、生长和采食量、肝脏酶活性以及血浆代谢物。在7至28日龄时，饲喂较低粗蛋白水平日粮的鸡体型较小，生长效率较低。在28至40日龄时给这些鸡饲喂较高蛋白质日粮可提高生长和饲料效率。饲喂较低蛋白质日粮的鸡的脂肪生成也更多，血浆胰岛素样生长因子-I（IGF-I）水平更低。当日粮处理转换时，随着鸡从高蛋白日粮转换为低蛋白日粮以及从低蛋白日粮转换为高蛋白日粮，脂肪生成分别增加和减少。在转换后4天观察到半最大变化，在转换后7天观察到最大变化。相比之下，当日粮处理转换时，随着鸡从高蛋白日粮转换为低蛋白日粮以及从低蛋白日粮转换为高蛋白日粮，血浆IGF-I分别减少和增加。在转换后2天观察到半最大变化。在所监测的三种肝脏酶中，苹果酸酶活性最紧密地跟随体外脂肪生成的快速变化。血浆IGF-I可能比中间代谢的变化更能敏感地指示日粮蛋白质的变化。
