The progress in our understanding of the endogenous protein concept over the past century is reviewed. Non-dietary proteins found in the digesta at the terminal ileum of poultry, known as endogenous protein loss, are comprised of digestive secretions, mucus and sloughed gut epithelial cells. The measurement of this loss is of fundamental importance because it is an indicator of gut metabolism and is essential to adjust apparent estimates of ileal amino acid digestibility. The ileal endogenous amino acid losses comprise of two components, namely basal and specific losses. The basal losses are fixed and associated with feed dry matter intake, whereas the specific losses are variable and induced by the presence of dietary components such as fibre and anti-nutrients. Currently there is no methodology available to directly measure the specific endogenous losses and these losses are calculated by determining the basal and total (basal plus specific) losses and, then subtracting the basal losses from total losses. The seminal features, specific applications and shortcomings of available methodologies are briefly outlined as well as the practical challenges faced in using the published endogenous amino acid loss values for true digestibility corrections. The relevance of taurine as a component of endogenous protein flow in poultry is identified for the first time.

中文翻译：

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家禽回肠内源氨基酸流动研究进展


回顾了过去一个世纪我们对内源蛋白质概念的理解进展。家禽回肠末端食糜中发现的非膳食蛋白质（称为内源性蛋白质损失）由消化分泌物、粘液和脱落的肠上皮细胞组成。这种损失的测量至关重要，因为它是肠道代谢的指标，并且对于调整回肠氨基酸消化率的表观估计至关重要。回肠内源氨基酸损失由两部分组成，即基础损失和特异性损失。基础损失是固定的，与饲料干物质摄入量相关，而具体损失是可变的，由膳食成分（如纤维和抗营养素）的存在引起。目前，没有可用于直接测量特定内源损失的方法，这些损失是通过确定基础损失和总损失（基础损失加上特定损失），然后从总损失中减去基础损失来计算的。简要概述了现有方法的重要特征、具体应用和缺点，以及使用已发表的内源氨基酸损失值进行真正的消化率校正时面临的实际挑战。牛磺酸作为家禽内源性蛋白质流的一个组成部分的相关性首次被确定。