Gebhardt G, Köhler R, Zebrowska T
Arch Tierernahr. 1978 Jan;28(1):11-20. doi: 10.1080/17450397809428210.
Three female pigs provided with re-entrant canulas at the beginning and the end of the small intestine and catheterized for blood and urine collection were once fed a 15N-labelled mixed diet. Until 48 hours after feed intake chyme from the canulas and urine and blood were collected at varying intervals. All 15N-frequencies measured in the duodenal chyme were found to be below the labelling of the feed protein. Until 11 hours after intake of the labelled feed, the residue obtained by centrifugation of the intestinal contents revealed the highest 15N-labelling. Only slight differences were found in the frequencies of the other fractions (proteins, peptides, free amino acids). The almost constant labelling of all fractions in that period is indicative of a dilution with endogenous nitrogen being constant in comparison with food N. The 15N-frequencies of the chyme fractions observed at the end of the small intestine allowed to conclude that the breakdown of the food proteins is more complete than the disintegration of the endogenous proteins.
三只在小肠起始端和末端安装了再进入式插管并通过插管收集血液和尿液的雌性猪，曾被喂食一次15N标记的混合饲料。在采食后48小时内，以不同间隔收集插管处的食糜以及尿液和血液。发现十二指肠食糜中测得的所有15N频率均低于饲料蛋白质的标记频率。在摄入标记饲料后11小时内，通过对肠内容物进行离心获得的残渣显示出最高的15N标记。在其他组分（蛋白质、肽、游离氨基酸）的频率上仅发现了细微差异。在此期间所有组分几乎恒定的标记表明，与食物氮相比，内源性氮的稀释是恒定的。在小肠末端观察到的食糜组分的15N频率可以得出结论，食物蛋白质的分解比内源性蛋白质的分解更完全。
