由于内源脂肪损失（ELF）的存在导致脂肪的表观回肠或全肠道消化率不能真实反映猪对脂肪的生物学利用率。如果用真回肠消化率来评价油脂的消化性则不会出现这种情况。但要测定脂肪的真回肠消化率，首先必须准确地测定ELF。关于ELF的研究不像对内源氨基酸的研究那样深入，目前的研究报道极少，有限的数据都是在对油脂的能值评价中顺便得到。这主要是由于测定内源脂肪损失的方法不确定，而且影响因素太复杂。然而，作为应用极广的高能饲料原料，在猪日粮配方中还没有脂肪的需要量标准，一个重要的原因就是缺乏脂肪真消化率数据。因此，有必要系统而全面地对脂肪内源损失进行研究与评定。本项目在本团队前期评价油脂原料能值的基础上，首先确定ELF的评定方法，然后在此基础上研究基础日粮类型、纤维水平及纤维源、脂肪存在形态对内源脂肪损失的影响，并测定13种常用油脂原料的回肠ELF，为将来评价油脂原料的真消化率而完善饲料原料数据库奠定基础。

The apparent ileal digestibility and apparent total tract digestibility of fats can not really reflect the bioavailability for pigs because of the presence of endogenous losses of fat (ELF). This does not happen if the true ileal digestibility is used to evaluate the digestibility of fats, while we must first accurately determine the ELF. The research on ELF is not as deep as the study of endogenous amino acids. The current research reports are rare, and the limited data are obtained in the evaluation of the energy value of lipids. Inconsistent method and complex influencing factors are the main reasons. However, lipid is widely used to feed industry as a high energy ingredient although there is no fat requirement in pig diet formula due to lack of the data of true ileal digestibility of fat. Thus, it is necessary to conduct a systematic and comprehensive study to evaluate the ELF. This project will investigate the effects of basal diets, fiber levels and fiber sources, lipid forms on, and determine the ileal ELF of 13 lipid ingredients based on our previous study on lipid energy evaluation, to provide the basis for estimating lipids true ileal digestibility and completing feedstuff database.