在不同阶段饲喂低蛋白日粮对生长猪骨骼肌内游离氨基酸组成和蛋白质合成途径的调控

畜牧编辑

　　2016. J. Anim. Sci. 94(12):5192-5205

　　在不同阶段饲喂低蛋白日粮对生长猪骨骼肌内游离氨基酸组成和蛋白质合成途径的调控

　　Y. H. Li, H. K. Wei, F. N. Li , S. W. Kim,C. Y. Wen, Y. H. Duan, Q. P. Guo, W. L. Wang, H. N. Liu and Y. L. Yin

　　本试验旨在探究保证生长猪肌蛋白沉积量不变的情况下日粮粗蛋白水平可降低的程度及其相关机制，以及试验猪对日粮蛋白受限所产生的反应是否受到后期饲养环节的影响而发生剧烈变化。选取36头试验猪（初始重为9.57±0.64 kg）分为两组置于独立的限位栏饲养10天或者是25天。每组猪只再分为3个小组，不同小组日粮的粗蛋白水平分别为20%、17%和14%。其中粗蛋白水平为17%和14%的日粮均补充Lys、Met、Thr和Trp，使日粮中以上四种氨基酸浓度与20%粗蛋白水平日粮相一致。试验结果表明与饲喂20%和17%粗蛋白水平日粮的猪只相比，饲喂14%粗蛋白日粮10天和25天后猪只的生长状况均受到显著抑制（P < 0.05）。

　　饲喂20%粗蛋白水平日粮25天后猪只血浆中尿素氮含量比饲喂17%和14%粗蛋白水平日粮的猪只要高。另外，饲喂低蛋白水平日粮25天后猪只骨骼肌中游离氨基酸水平有显著变化（P < 0.05）；值得注意的是，14%粗蛋白日粮与20%粗蛋白日粮相比可显著提高肌肉中游离氨基酸浓度。同时，日粮中粗蛋白水平的降低也影响了试验结束时骨骼肌内某些氨基酸转运载体的mRNA水平，尤其是14%和20%两种粗蛋白水平日粮组间存在极显著的差异。

　　最重要的是，我们发现给猪只饲喂14%粗蛋白日粮后其骨骼肌中雷帕霉素靶蛋白复合物1（mTORC1）通路相关基因得到全面的激活（P <0.05）。饲喂17%粗蛋白日粮的猪只与饲喂20%粗蛋白日粮的猪只相比只有部分基因受到抑制。然而，给猪只饲喂低蛋白水平日粮十天后我们发现血浆指标、肌肉中游离氨基酸浓度和肌肉中mTORC1 通路的变化极小。

　　总的来说，本试验的研究结果表明在14%粗蛋白日粮中补充限制性氨基酸并不能有效恢复猪只蛋白合成和肌肉生长，然而17%粗蛋白日粮可能会维持猪只的肌肉水平，而肌肉水平在部分程度上受到氨基酸转运载体表达量、游离氨基酸水平和mTORC1信号通路激活程度的调节。

　　Regulation in free amino acid profile and protein synthesis pathway of growing pig skeletal muscles by low-protein diets for different time periods

　　Y. H. Li, H. K. Wei, F. N. Li , S. W. Kim,C. Y. Wen, Y. H. Duan, Q. P. Guo, W. L. Wang, H. N. Liu and Y. L. Yin

　　The objective of the study was to explore the extent to which the dietary CP level can be reduced for maintaining muscle protein deposition in growing pigs as well as the related mechanism and whether the response to dietary protein restriction is diversely modified throughout the 2 trial periods. A total of 36 pigs (9.57 ± 0.64 kg initial BW) were individually penned and fed 1 of 3 diets for 10 or 25 d. During each period, the diets contained 20, 17, and 14% CP, respectively. Both the 17% CP diet and the 14% CP diet were supplemented with Lys, Met, Thr, and Trp to provide the same total concentrations as those in the 20% CP diet. Results showed that feeding the 14% CP diet for 10 or 25 d seriously impaired (P < 0.05) growth performance of the pigs compared with those fed the 20 or 17% CP diets. Pigs fed the 20% CP diet for 25 d had a higher (P < 0.05) serum content of urea nitrogen than those fed the 17 and 14% CP diets. In addition, the free AA (FAA) profile in skeletal muscle of the pigs was evidently changed (P < 0.05) by the low-protein diets for 25 d; of note, the 14% CP diet increased (P <0.05) the size of muscle FAA pool compared with the 20% CP diet. Meanwhile, ond 25, reducing dietary CP levels also influenced (P < 0.05) mRNA levels of specific AA transceptors expressed in skeletal muscle, especially revealing the striking differences between the 14 and 20% CP diet–fed pigs. Most importantly, we observed a globally decreased (P < 0.05) activation of the mammalian target of rapamycin complex 1 (mTORC1) pathway in skeletal muscle of pigs fed the 14% CP diet, whereas only partial inhibition was observed for those fed the 17% CP diet compared with those fed the 20% CP diet. However, feeding the low-protein diets for 10 d had minimal effects on serum parameters, muscle FAA profile, and muscle mTORC1 pathway of the pigs. Taken together, our results indicate that supplementing with limiting AA to the 14% CP diet is not highly effective for the pigs in restoring protein synthesis and muscle growth, whereas the 17% CP diet likely maintains the pigs’ muscle mass, which were regulated, at least in part, by mediating AA transceptors expression, FAA profile, and activation of the mTORC1 pathway。

翻译：李光燃 来源：猪营养国际论坛CSIS

山中的漫游者

也许以蛋白质屠宰率计算，低蛋白日粮并不是一个理想的方案。

山中的漫游者

也许以蛋白质屠宰率计算，低蛋白日粮并不是一个理想的方案。

山中的漫游者

也许以蛋白质屠宰率计算，低蛋白日粮并不是一个理想的方案。

山中的漫游者

也许以蛋白质屠宰率计算，低蛋白日粮并不是一个理想的方案。

山中的漫游者

也许以蛋白质屠宰率计算，低蛋白日粮并不是一个理想的方案。