^(15)N尿素在兔体内消化吸收及利用机理研究 Ⅰ.兔对^(15)N尿素利用的氮平衡状况及形态分配

Studies on the Mechanism of Absorption, Digestion and Utilization of 15 N urea in Rabbits I. Nitrogen Balance, Distribution and Forms of 15 N urea in Rabbits

应用稳定同位素１５Ｎ尿素示踪技术，经兔消化代谢试验，研究尿素氮平衡状况，测定其消化率和利用系数，并对在兔体内形成蛋白质沉积及其它含氮化合物形态与分配进行了讨论，肯定了尿素氮作为补充兔日粮中粗蛋白营养不足的价值。研究发现，１５Ｎ尿素在胃和小肠内容物中，具有与盲肠中相似的由微生物转化合成极易被兔消化利用的游离氨基酸１５Ｎ和蛋白质１５Ｎ等化合物的功能，从而促进了兔对日粮尿素的消化吸收和利用。

This paper dealt with the metabolism of 15 N labelled urea in rabbits body by using 15 N tracer technique. 2 5 kg weight and 3 months old New Zealand white male rabbits were chosen for this experiment. The basal diet which contained 13 48% of curde protein was fed to the rabbits for 120 g per day with additive 1% of 15 N urea(1 2000 g) . Results were as follows: ①Nitrogen balance value of urea was (98 3±12 4)mg per day which were 18 2%±1 85% to the 15 N urea intake content. ②Apparent digestibility and utilization coefficient of 15 N were 87 8%±1 4% and 20 7%±8 4%, respectively, so it could be used as a supplement when lack of crude protein in the basal diet. ③There were 90 6% and 9 4% of 15 N in protein nitrogen and nonprotein nitrogen in the rabbits blood, respectively, while there were 74%±12% 15 N in protein and 2 0%-6 9% 15 N in free amino acid in the organs. ④It was also observed that intake of 15 N urea could not only convert into protein and free amino acid in caecum content(81 1%), but also increase the proportion of 15 N which were 74.6% and 76.3% in protein and amino acid in stomach and small intestine content, respectively. It was referred that 15 N urea could be synthesized by microorganism to 15 N free amino acid and 15 N protein, which had been proved in the experiment.