Terrill T H, Waghorn G C, Woolley D J, McNabb W C, Barry T N
Department of Animal Science, Massey University, Palmerston North, New Zealand.
Br J Nutr. 1994 Sep;72(3):467-77. doi: 10.1079/bjn19940048.
Three experiments were conducted to determine the fate of condensed tannins (CT) during digestion in sheep. CT were measured as extractable, protein-bound and fibre-bound fractions using the butanol-HCl procedure. In Expt 1, purified CT were added to digesta from different parts of the digestive tract obtained from a pasture-fed sheep. Recoveries of CT after 0 and 4 h of anaerobic incubation at 39 degrees averaged: rumen 78.9 and 57.5%; abomasum 50.9 and 49.0%; duodenum 64.4 and 46.0% and ileum 43.4 and 38.8%. In Expt 2, [14C]CT was given per abomasum over a 6.5 h period at 15 min intervals to a sheep previously fed on Lotus pedunculatus (which contains CT). The sheep was killed at the end of the period and 92.4% of the label was recovered. Virtually all of the label was in the digesta, and none was detected in the blood, so that the CT-carbon appeared not to be absorbed from the small intestine. In Expt 3, rumen, abomasal and ileal digesta and faeces samples from sheep fed on Lotus pedunculatus were analysed for CT and CT flow along the digestive tract calculated from reference to indigestible markers. Values were low in all digesta samples, indicating disappearance of CT across the rumen and small intestine, and CT recovery in faeces was only about 15% of intake. However, the 14C results from Expt 2 suggested that little if any CT-carbon was absorbed and the low recoveries in Expt 1 are considered to be a consequence of either conformational changes to the CT molecule such that it is no longer detectable by colorimetric methods, an inability of the analytical method to release bound CT for the butanol-HCl assay, or interference from other digesta constituents. It is concluded that the butanol-HCl method of CT analysis is appropriate for quantifying CT in herbages but not in digesta or faeces, and that a substantial part of CT released during protein digestion in the small intestine may not be detectable by normal CT analytical methods.
进行了三项实验以确定绵羊消化过程中缩合单宁（CT）的去向。使用正丁醇 - 盐酸法将CT测定为可提取、与蛋白质结合和与纤维结合的部分。在实验1中，将纯化的CT添加到从以牧草饲养的绵羊获得的消化道不同部位的消化物中。在39℃厌氧培养0和4小时后，CT的回收率平均为：瘤胃78.9%和57.5%；皱胃50.9%和49.0%；十二指肠64.4%和46.0%；回肠43.4%和38.8%。在实验2中，以15分钟的间隔，通过皱胃向一只先前以百脉根（含有CT）为食的绵羊在6.5小时内给予[14C]CT。在该时间段结束时处死绵羊，回收了92.4%的标记物。实际上所有的标记物都在消化物中，在血液中未检测到，因此CT - 碳似乎未从小肠吸收。在实验3中，分析了以百脉根为食的绵羊的瘤胃、皱胃和回肠消化物以及粪便样本中的CT，并根据不可消化标记物计算了沿消化道的CT流量。所有消化物样本中的值都很低，表明CT在瘤胃和小肠中消失，粪便中的CT回收率仅为摄入量的约15%。然而，实验2的14C结果表明，几乎没有CT - 碳被吸收，实验1中的低回收率被认为是由于CT分子的构象变化导致其不再能用比色法检测到，分析方法无法释放与蛋白质结合的CT用于正丁醇 - 盐酸测定，或者受到其他消化物成分的干扰。得出的结论是，CT分析的正丁醇 - 盐酸法适用于定量牧草中的CT，但不适用于消化物或粪便中的CT，并且在小肠蛋白质消化过程中释放的很大一部分CT可能无法通过常规CT分析方法检测到。
