Macelline Shemil P, Selle Peter H, Toghyani Mehdi, Liu Sonia Y
School of Life and Environmental Sciences, Faculty of Science, The University of Sydney, Camperdown, NSW 2006, Australia; Poultry Research Foundation, The University of Sydney, Camden, NSW 2570, Australia.
Poultry Research Foundation, The University of Sydney, Camden, NSW 2570, Australia; Sydney School of Veterinary Science, The University of Sydney, Camperdown, NSW 2006, Australia.
Poult Sci. 2025 Apr 19;104(7):105199. doi: 10.1016/j.psj.2025.105199.
This review highlights that utilization of dietary amino acids for energy metabolism in broiler chickens imposes a metabolic cost, as their primary role is to support body protein synthesis. This issue becomes more critical in reduced-crude protein (CP) diets. When amino acids are used as fuel for enterocytes or undergo catabolism in the liver, they are diverted from body protein accretion. Catabolism of amino acids for energy generates α-keto acids and ammonia. α-Keto acids can be fully oxidized to produce ATP or converted into pyruvate, ketone bodies, and intermediates of the tricarboxylic acid cycle. Meanwhile, ammonia must be detoxified through the uric acid cycle, a process that requires energy, glycine, and aspartic acid. Derivatives of α-keto acids can contribute to gluconeogenesis and de novo lipogenesis, leading to glucose and fatty acid synthesis, respectively. The α-keto acid derivatives are more likely to undergo de novo lipogenesis in broilers, as evidenced by consolidated data in this review. However, de novo lipogenesis is also an energy-intensive process. Therefore, enhancing the efficiency of dietary amino acid conversion to body protein requires reducing their utilization for energy metabolism. This may be achieved through dietary manipulations, as previous studies indicate that amino acid catabolism in enterocytes and the liver is influenced by starch and protein digestive dynamics, dietary amino acid compositions, and the primary feed grain used in diets. In reduced-CP broiler diets, supplementation of glutamic acid and potentially glutamine, aspartic acid, and proline could mitigate the catabolism of essential amino acids in enterocytes. Additionally, moderating starch digestion rates may reduce amino acid catabolism in enterocytes. Moreover, optimizing the balance of dietary protein-bound and non-bound amino acids could minimize amino acid catabolism in the liver. In summary, reducing the contribution of amino acids to energy metabolism in broiler chickens is particularly beneficial in reduced-CP diets, ultimately supporting more sustainable chicken meat production.
本综述强调，肉鸡利用膳食氨基酸进行能量代谢会产生代谢成本，因为它们的主要作用是支持机体蛋白质合成。在低粗蛋白（CP）日粮中，这个问题变得更加关键。当氨基酸被用作肠细胞的燃料或在肝脏中进行分解代谢时，它们就会从机体蛋白质积累中被转移。氨基酸分解代谢产生能量会生成α-酮酸和氨。α-酮酸可以被完全氧化以产生ATP，或转化为丙酮酸、酮体和三羧酸循环的中间产物。与此同时，氨必须通过尿酸循环进行解毒，这一过程需要能量、甘氨酸和天冬氨酸。α-酮酸的衍生物可有助于糖异生和从头脂肪生成，分别导致葡萄糖和脂肪酸的合成。本综述中的综合数据表明，α-酮酸衍生物在肉鸡中更有可能进行从头脂肪生成。然而，从头脂肪生成也是一个能量密集型过程。因此，提高膳食氨基酸转化为机体蛋白质的效率需要减少它们用于能量代谢的比例。这可以通过日粮调控来实现，因为先前的研究表明，肠细胞和肝脏中的氨基酸分解代谢受淀粉和蛋白质消化动态、日粮氨基酸组成以及日粮中使用的主要谷物饲料的影响。在低CP肉鸡日粮中，补充谷氨酸以及可能的谷氨酰胺、天冬氨酸和脯氨酸可以减轻肠细胞中必需氨基酸的分解代谢。此外，调节淀粉消化率可能会降低肠细胞中的氨基酸分解代谢。而且，优化日粮中与蛋白质结合和未结合氨基酸的平衡可以使肝脏中的氨基酸分解代谢降至最低。总之，在低CP日粮中减少氨基酸对能量代谢的贡献对肉鸡特别有益，最终支持更可持续的鸡肉生产。
