Department of Animal Science, Texas A&M University, College Station, TX, USA.
North American Renderers Association, Alexandria, VA, USA.
Adv Exp Med Biol. 2021;1285:109-131. doi: 10.1007/978-3-030-54462-1_7.
Both poultry meat and eggs provide high-quality animal protein [containing sufficient amounts and proper ratios of amino acids (AAs)] for human consumption and, therefore, play an important role in the growth, development, and health of all individuals. Because there are growing concerns about the suboptimal efficiencies of poultry production and its impact on environmental sustainability, much attention has been paid to the formulation of low-protein diets and precision nutrition through the addition of low-cost crystalline AAs or alternative sources of animal-protein feedstuffs. This necessitates a better understanding of AA nutrition and metabolism in chickens. Although historic nutrition research has focused on nutritionally essential amino acids (EAAs) that are not synthesized or are inadequately synthesized in the body, increasing evidence shows that the traditionally classified nutritionally nonessential amino acids (NEAAs), such as glutamine and glutamate, have physiological and regulatory roles other than protein synthesis in chicken growth and egg production. In addition, like other avian species, chickens do not synthesize adequately glycine or proline (the most abundant AAs in the body but present in plant-source feedstuffs at low content) relative to their nutritional and physiological needs. Therefore, these two AAs must be sufficient in poultry diets. Animal proteins (including ruminant meat & bone meal and hydrolyzed feather meal) are abundant sources of both glycine and proline in chicken nutrition. Clearly, chickens (including broilers and laying hens) have dietary requirements for all proteinogenic AAs to achieve their maximum productivity and maintain optimum health particularly under adverse conditions such as heat stress and disease. This is a paradigm shift in poultry nutrition from the 70-year-old "ideal protein" concept that concerned only about EAAs to the focus of functional AAs that include both EAAs and NEAAs.
家禽肉和蛋都为人类提供高质量的动物蛋白质[含有足够数量和适当比例的氨基酸（AA）]，因此在家禽的生长、发育和健康中起着重要作用。由于人们越来越关注家禽生产的低效率及其对环境可持续性的影响，因此人们非常关注低蛋白日粮的配方和通过添加低成本晶体氨基酸或替代动物蛋白饲料来源的精准营养。这需要更好地了解鸡的 AA 营养和代谢。虽然历史营养研究主要集中在不能或不能在体内充分合成的营养必需氨基酸（EAA）上，但越来越多的证据表明，传统上分类为非营养必需氨基酸（NEAA）的谷氨酸和谷氨酸等，除了蛋白质合成外，在鸡的生长和产蛋中还有其他生理和调节作用。此外，与其他禽类一样，鸡相对于其营养和生理需求，不能充分合成甘氨酸或脯氨酸（体内最丰富的 AA，但在植物源饲料中的含量较低）。因此，这两种 AA 必须在禽类日粮中充足。动物蛋白（包括反刍动物肉骨粉和水解羽毛粉）是鸡营养中甘氨酸和脯氨酸的丰富来源。显然，鸡（包括肉鸡和蛋鸡）需要所有蛋白质氨基酸来实现其最大生产力并保持最佳健康，特别是在热应激和疾病等不利条件下。这是家禽营养从 70 年前只关注 EAA 的“理想蛋白质”概念到关注包括 EAA 和 NEAA 的功能性 AA 的范式转变。
