Rosebrough R W, Richards M P, McMurtry J P
Growth Biology Laboratory, Animal and Natural Resources Institute, United States Department of Agriculture--Agricultural Research Service, Beltsville Agricultural Research Center, Beltsville, MD 20705, USA.
Growth Dev Aging. 2004 Summer;68(1):19-32.
Although changes in dietary protein levels change metabolism in the broiler chicken, there is little information concerning the time course of the process of adaptation. Therefore, male Hubbard broiler chickens were fed diets containing either 12 or 30% crude protein from 7 to 28 d of age and then were switched to the opposite level for an additional 9 d. Birds were bled and killed at 0, 2, 5, 7and 9 d following the reversals. Data taken at these intervals included those involved in vitro lipogenesis (IVL), growth and feed consumption, hepatic enzyme activities and plasma hormones and metabolites. Birds fed the lower level of crude protein were smaller in growth from 7 to 28 d. Feeding these birds a higher protein diet from 28 to 37 d improved both growth and feed efficiency in comparison to controls. 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 and low to high protein diets, respectively. Half-maximal changes were observed 2 d after the reversal and maximal changes 5 d after the reversal. In contrast, switching dietary treatments decreased and increased plasma IGF-I as birds were switched from high to low and 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 IVL. In the present study, plasma IGF-I may be a more sensitive indicator of changes in dietary protein than changes in intermediary metabolism.
虽然日粮蛋白质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，雄性哈伯德肉鸡从7日龄到28日龄饲喂含12%或30%粗蛋白的日粮，然后再换成相反水平的日粮，持续9天。在日粮转换后的0、2、5、7和9天对鸡进行采血并宰杀。在这些时间间隔采集的数据包括体外脂肪生成（IVL）、生长和采食量、肝脏酶活性以及血浆激素和代谢产物等方面的数据。饲喂较低粗蛋白水平日粮的鸡在7至28日龄时生长较慢。与对照组相比，在28至37日龄给这些鸡饲喂较高蛋白日粮可提高生长速度和饲料效率。饲喂较低蛋白日粮的鸡的脂肪生成也更多，而血浆胰岛素样生长因子-I（IGF-I）则较少。当日粮处理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时，脂肪生成分别增加和减少。在日粮转换后2天观察到变化达到一半最大值，在转换后5天观察到最大变化。相比之下，当日粮处理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时，血浆IGF-I分别减少和增加。在日粮转换后2天观察到变化达到一半最大值。在所监测的三种肝脏酶中，苹果酸酶活性与IVL的快速变化最为密切相关。在本研究中，血浆IGF-I可能比中间代谢的变化更能敏感地反映日粮蛋白质的变化。
