Liao Shengfa F, Wang Taiji, Regmi Naresh
Department of Animal and Dairy Sciences, Mississippi State University, Mississippi State, MS 39762 USA.
Springerplus. 2015 Mar 27;4:147. doi: 10.1186/s40064-015-0927-5. eCollection 2015.
Improving feed efficiency of pigs with dietary application of amino acids (AAs) is becoming increasingly important because this practice can not only secure the plasma AA supply for muscle growth but also protect the environment from nitrogen discharge with feces and urine. Lysine, the first limiting AA in typical swine diets, is a substrate for generating body proteins, peptides, and non-peptide molecules, while excess lysine is catabolized as an energy source. From a regulatory standpoint, lysine is at the top level in controlling AA metabolism, and lysine can also affect the metabolism of other nutrients. The effect of lysine on hormone production and activities is reflected by the change of plasma concentrations of insulin and insulin-like growth factor 1. Lysine residues in peptides are important sites for protein post-translational modification involved in epigenetic regulation of gene expression. An inborn error of a cationic AA transporter in humans can lead to a lysinuric protein intolerance condition. Dietary deficiency of lysine will impair animal immunity and elevate animal susceptibility to infectious diseases. Because lysine deficiency has negative impact on animal health and growth performance and it appears that dietary lysine is non-toxic even at a high dose of supplementation, nutritional emphasis should be put on lysine supplementation to avoid its deficiency rather than toxicity. Improvement of muscle growth of monogastric animals such as pigs via dietary lysine supply may be due to a greater increase in protein synthesis rather than a decrease in protein degradation. Nevertheless, the underlying metabolic and molecular mechanisms regarding lysine effect on muscle protein accretion merits further clarification. Future research undertaken to fully elucidate the metabolic and regulatory mechanisms of lysine nutrition could provide a sound scientific foundation necessary for developing novel nutritional strategies to enhance the muscle growth and development of meat animals.
通过在日粮中应用氨基酸（AA）来提高猪的饲料效率变得越来越重要，因为这种做法不仅可以确保血浆氨基酸供应以促进肌肉生长，还可以保护环境免受粪便和尿液中氮排放的影响。赖氨酸是典型猪日粮中的第一限制性氨基酸，是生成身体蛋白质、肽和非肽分子的底物，而过量的赖氨酸则作为能量来源被分解代谢。从调节的角度来看，赖氨酸在控制氨基酸代谢方面处于最高水平，并且赖氨酸还可以影响其他营养素的代谢。赖氨酸对激素产生和活性的影响通过胰岛素和胰岛素样生长因子1血浆浓度的变化来反映。肽中的赖氨酸残基是参与基因表达表观遗传调控的蛋白质翻译后修饰的重要位点。人类阳离子氨基酸转运蛋白的先天性缺陷可导致赖氨酸尿性蛋白不耐受症。日粮中赖氨酸缺乏会损害动物免疫力并提高动物对传染病的易感性。由于赖氨酸缺乏对动物健康和生长性能有负面影响，而且即使在高剂量补充时日粮中的赖氨酸似乎也是无毒的，因此营养方面应强调补充赖氨酸以避免其缺乏而非毒性。通过日粮供应赖氨酸来改善猪等单胃动物的肌肉生长，可能是由于蛋白质合成的增加幅度大于蛋白质降解的减少幅度。然而，赖氨酸对肌肉蛋白质积累影响的潜在代谢和分子机制仍有待进一步阐明。未来为充分阐明赖氨酸营养的代谢和调节机制而进行的研究，可以为开发新的营养策略以促进肉用动物的肌肉生长和发育提供必要的坚实科学基础。
