Characterizing the effects of dietary and endogenous factors on amino acid requirements of fish

大宗商品价格高企有力地推动了饲料生产商把重点放在提高鱼饲料的成本效益上。鱼饲料制造商大幅降低了鱼粉水平，并在饲料中更多地依赖更经济的蛋白质来源。这种对不同(较差)氨基酸组成的蛋白质来源的日益依赖，带来了对鱼类必需氨基酸(EAA)需求的更多关注。对文献的批判性回顾表明，我们对鱼的氨基酸营养的理解存在着非常显著的差距。关于鱼类必需氨基酸(EAA)需要量的最佳水平和最佳表达方式，有多种意见。这种情况往往限制了饲料制造商有意义地提高饲料成本效益和/或调整饲料配方以适应不断变化的商品市场的能力(例如，蛋白质来源相对于脂肪来源的价格相对较低)。观点冲突的根本原因似乎是我们对内源因素(如物种、生命阶段)和饮食因素对鱼类对EAA的利用和需求的影响缺乏了解。鱼类氨基酸分解代谢的调节也可能与单胃陆生动物略有不同。为猪和家禽开发的模型适应鱼类营养导致预测不佳，特别是对大型虹鲑鱼。

High commodity prices created a strong impetus for feed manufacturer to focus on improving cost-effectiveness of fish feeds. Fish feed manufacturers have significantly reduced fish meal level and have been relying more heavily on more economical protein sources in their feeds. This increased reliance on protein sources with different (poorer) amino acid profiles has brought about the need to pay greater attention to the essential amino acids (EAA) requirements of fish. A critical review of the literature reveals very significant gaps in our understanding of amino acid nutrition of fish. There is a multitude of opinions as to the optimal levels and best mode of expression of essential amino acid (EAA) requirements for fish. This situation often limits the ability of feed manufacturers to meaningfully improve the cost-effectiveness of feeds and/or adapt feed formulations to a changing commodities market (e.g. relative low price of protein sources compared to lipid sources). The root cause of the conflicting views appears to be our poor understanding of the effect of endogenous (e.g., species, life stage) and dietary factors on EAA utilization and requirements of fish. The regulation of amino acid catabolism of fish may also be slightly different from that of monogastric terrestrial animals. The adaptation of models developed for swine and poultry to fish nutrition resulted in poor predictions, notably for large rainbow trout.