使用氨氮替换生长猪日粮中的非必需氨基酸不会影响胴体沉积蛋白的氨基酸组成

IMCTT

　　2017. J. Anim. Sci. 95(10): 4481-4489
　　使用氨氮替换生长猪日粮中的非必需氨基酸不会影响胴体沉积蛋白的氨基酸组成
　　W. D. Mansilla, J. K. Htoo and C. F. M. de Lange

　　氨基酸用于机体蛋白质的沉积，因此沉积蛋白的氨基酸组成是决定动物生长阶段氨基酸需要量的重要指标。本试验的主要目的在于研究缺乏非必需氨基酸的日粮中添加氨氮对生长猪氮沉积和机体氨基酸组成的影响。试验选用48头去势公猪，初始重13.6±0.7kg。试验开始时屠宰8头检测初始蛋白质量。剩下40头随机饲喂以下5中日粮中的一种：1、负对照，95%基础日粮+5%玉米淀粉（基础日粮为满足所有必须氨基酸需要量，但是缺乏非必需氨基酸态氮，8.01%粗蛋白含量）；2、低氨氮组，95%基础日粮+5%氨氮，氨氮提供额外1.35%粗蛋白；3、高氨氮组，95%基础日粮+5%氨氮，氨氮提供额外2.7%粗蛋白；4、低非必需氨基酸组，95%基础日粮+5%非必需氨基酸，非必需氨基酸提供额外1.35%粗蛋白；5、高非必需氨基酸组，95%基础日粮+5%非必需氨基酸，非必需氨基酸提供额外2.7%粗蛋白。高非必需氨基酸组日粮的标准回肠可消化非必需氨基酸含量与20kg猪的非必需氨基酸组成类似，并且推测可以降低非必需氨基酸的内源合成。猪每天饲喂3次，饲喂量为3倍代谢能维持需要量。3周试验期过后，屠宰猪只，收集胴体、内脏器官并称重、冷冻、粉碎，检测其中蛋白质质量。分析初始猪只、负对照组、高氨氮组、高非必需氨基酸组胴体和内脏中氨基酸组成，计算总氨基酸、沉积的氨基酸、日粮氨基酸效率和最小非必需氨基酸合成量。随着氮提供量的增加，胴体重和机体氮沉积线性提高（P＜0.05）。不同氮源组猪只胴体重氨基酸组成和蛋白质沉积量没有显著差异（P＞0.10），但是非必需氨基酸组中内脏器官中和沉积的蛋白中胱氨酸的含量显著增加（P＜0.05）。随着氮提供量的增加，可消化必需氨基酸的沉积效率明显提高（P＜0.05），但是不同氮源之间没有显著差异（P＞0.10）。氨氮组非必需氨基酸的合成量显著高于添加非必需氨基酸组。总之，缺乏非必需氨基酸的日粮中添加氨氮可以提高氮沉积，而不影响胴体氨基酸组成。

　　Replacing dietary non essential amino acids with ammonia nitrogen does not alter amino acid profile of deposited protein in the carcass of growing pigs fed a diet deficient in non essential amino acid nitrogen

　　W. D. Mansilla, J. K. Htoo and C. F. M. de Lange

　　Amino acid usage for protein retention, and, consequently, the AA profile of retained protein, is the main factor for determining AA requirements in growing animals. The objective of the present study was to determine the effect of supplementing ammonia N on whole-body N retention and the AA profile of retained protein in growing pigs fed a diet deficient in nonessential AA (NEAA) N. In total, 48 barrows with a mean initial BW of 13.6 kg (SD 0.7) were used. At the beginning of the study, 8 pigs were euthanized for determination of initial protein mass. The remaining animals were individually housed and fed 1 of 5 dietary treatments. A common basal diet (95% of experimental diets) was formulated to meet the requirements for all essential AA (EAA) but to be deficient in NEAA N (CP = 8.01%). The basal diet was supplemented (5%) with corn starch (negative control) or 2 N sources (ammonia or NEAA) at 2 levels each to supply 1.35 or 2.70% extra CP. The final standardized ileal digestible (SID) NEAA content in the high-NEAA-supplemented diet (positive control) was based on the NEAA profile of whole-body protein of 20-kg pigs, and it was expected to reduce the endogenous synthesis of NEAA. Pigs were fed at 3.0 times maintenance energy requirements for ME in 3 equal meals daily. At the end of a 3-wk period, pigs were euthanized and the carcass and visceral organs were weighed, frozen, and ground for determination of protein mass. From pigs in the initial, negative control, high-ammonia, and high-NEAA groups, AA contents in the carcass and pooled visceral organs were analyzed to determine the total and deposited protein AA profile, dietary EAA efficiencies, and minimal de novo synthesis of NEAA. Carcass weight and whole-body N retention linearly increased (P < 0.05) with N supplementation. The AA profile of protein and deposited protein in the carcass was not different (P > 0.10) between N sources, but Cys content increased (P <0.05) with NEAA compared with ammonia in visceral organ protein and deposited protein. The dietary SID EAA efficiency for increasing EAA deposition in whole-body protein increased (P < 0.05) with N supplementation, but it was not different (P > 0.10) between N sources. The de novo synthesis of NEAA increased (P < 0.05) for ammonia compared with NEAA supplementation. In conclusion, adding ammonia as a N source to diets deficient in NEAA N increases whole-body N retention without affecting the carcass AA profile.

　　翻译：朱滔 猪营养国际论坛CSIS