Macelline Shemil P, Liu Sonia Y, Selle Peter H
School of Life and Environmental Sciences, Faculty of Science, The University of Sydney, Camperdown 2006, NSW, Australia.
Poultry Research Foundation, The University of Sydney, Camden 2570, NSW, Australia.
Anim Nutr. 2025 Jul 12;22:201-213. doi: 10.1016/j.aninu.2025.05.004. eCollection 2025 Sep.
A dietary protein intake of approximately 2.5 kg is required to generate 1.0 kg of protein in the carcass of broiler chickens at 42 d post-hatch, reflecting the attrition or wastage of dietary amino acids that occurs during their lifespan. Thus, the aim of this review is to examine amino acid utilisation in broilers because the identification and correction of any avoidable losses will advantage both the chicken meat industry and consumers. Amino acids are lost to catabolic pathways in their transition across the enterocytes for energy production required for digestive processes. However, slowly digestible starch has been indicated to spare amino acids from catabolic losses by providing more glucose as an alternative energy substrate. This potential benefit warrants further investigation. Protein turnover may represent an even greater source of amino acid attrition, but it is a complex area. Protein turnover refers to the dynamic equilibrium between protein deposition and degradation, with a positive balance indicating net protein synthesis and growth. 3-Methylhistidine concentrations in systemic plasma may be a sufficiently accurate indicator of protein degradation, which is probably the more influential component in protein turnover. If this can be demonstrated, experiments involving both L-carnitine and 3-methylhistidine may prove highly instructive because there are indications that L-carnitine has the capacity to depress protein degradation and enhance protein turnover in broiler chickens. The function of insulin in avian species is essentially a conundrum, particularly in relation to its regulatory role over protein turnover as broilers mature, and, ideally, this should be elucidated. Importantly, nutritionists should continue to endeavour to formulate diets for broiler chickens that meet amino acid requirements accurately. When this is achieved, circulating ammonia levels arising from post-enteral amino acid imbalances will be limited to the advantage of protein turnover and broiler growth performance. It is possible that protein degradation would be attenuated by broiler diets with appropriate balances between protein-bound and non-bound entities, ideal amino acid ratios and higher dietary electrolyte balances.
孵化后42天的肉鸡，要在胴体中生成1.0千克蛋白质，大约需要摄入2.5千克膳食蛋白质，这反映了膳食氨基酸在其生命周期中出现的损耗或浪费。因此，本综述的目的是研究肉鸡的氨基酸利用情况，因为识别并纠正任何可避免的损失将对鸡肉行业和消费者都有利。氨基酸在穿过肠细胞的过程中会进入分解代谢途径，以产生消化过程所需的能量。然而，有研究表明，缓慢消化的淀粉可以通过提供更多葡萄糖作为替代能量底物，从而避免氨基酸的分解代谢损失。这种潜在益处值得进一步研究。蛋白质周转可能是氨基酸损耗的更大来源，但这是一个复杂的领域。蛋白质周转是指蛋白质沉积和降解之间的动态平衡，正平衡表示净蛋白质合成和生长。全身血浆中3-甲基组氨酸的浓度可能是蛋白质降解的一个足够准确的指标，而蛋白质降解可能是蛋白质周转中更具影响力的组成部分。如果能够证明这一点，涉及左旋肉碱和3-甲基组氨酸的实验可能会极具启发性，因为有迹象表明左旋肉碱有能力抑制肉鸡的蛋白质降解并提高其蛋白质周转。胰岛素在禽类中的功能基本上是一个谜，特别是在肉鸡成熟过程中其对蛋白质周转的调节作用方面，理想情况下，这一点应该得到阐明。重要的是，营养学家应继续努力为肉鸡配制能准确满足氨基酸需求的日粮。当做到这一点时，肠后氨基酸失衡产生的循环氨水平将受到限制，这有利于蛋白质周转和肉鸡的生长性能。具有适当的蛋白质结合和非结合实体平衡、理想氨基酸比例和更高日粮电解质平衡的肉鸡日粮，有可能会减弱蛋白质降解。
