氮在马消化道中的分配

J Anim Sci. 1983 Oct;57(4):943-53. doi: 10.2527/jas1983.574943x.

Twelve adult horses were fed a corn-oats-timothy hay diet containing 2.87% nitrogen (N) for 4 wk and were then killed. Fresh digesta samples were immediately harvested from the stomach, duodenum, jejunum, ileum, cecum, large colon, small colon, rectum and feces. Total N content of the digesta (on a dry matter basis) increased from the stomach (2.74%) to the duodenum (5.58%; P less than .01), decreased in the cecum (3.10%, P less than .01), remained constant through the large intestine and decreased in the feces (2.10%; P less than .01). High-speed centrifugation of wet digesta and low-speed centrifugation following tungstic acid treatment of wet digesta were comparable in their effectiveness in separating water soluble N-containing compounds (S-N) from insoluble N-containing compounds (P-N). The P-N was further partitioned into neutral detergent soluble (NDS-N) and neutral detergent insoluble (NDF-N) fractions. The NDF-N constituted from 6 to 17% of the total digesta N at any location along the digestive tract. The S-N constituted about 20% of the total digesta N in the stomach, increased to about 80% at mid-jejunum (P less than .01), decreased to 30% in the cecum (P less than .01) and increased throughout the large intestine. The calculation of cumulative apparent digestibilities indicated that total digesta N underwent net disappearance along the entire tract, except in the duodenum. Dietary NDF-N underwent net disappearance throughout the digestive tract. The NDS-N portion of the P-N disappeared in the duodenum, jejunum and small colon, but underwent net appearance in the ileum, cecum and large colon. There was a net appearance of S-N in the duodenum and net disappearances in the ileum and cecum. The shifts in N partitioning along the lower digestive tract and the decreases in N concentrations suggest that the jejunum, ileum, cecum and small colon are major sites of the net absorption of N and that much of the N absorbed in the small colon was supplied by the conversion of NDS-N to S-N.

给12匹成年马喂食含2.87%氮（N）的玉米-燕麦-梯牧草日粮，持续4周，然后将其宰杀。立即从胃、十二指肠、空肠、回肠、盲肠、大结肠、小结肠、直肠和粪便中采集新鲜消化物样本。消化物的总氮含量（以干物质计）从胃中的2.74%增加到十二指肠中的5.58%（P<0.01），在盲肠中降低（3.10%，P<0.01），在整个大肠中保持恒定，在粪便中降低（2.10%；P<0.01）。湿消化物的高速离心和钨酸处理湿消化物后的低速离心在从含氮不溶性化合物（P-N）中分离水溶性含氮化合物（S-N）方面效果相当。P-N进一步分为中性洗涤剂可溶性（NDS-N）和中性洗涤剂不溶性（NDF-N）部分。在消化道的任何位置，NDF-N占总消化物氮的6%至17%。S-N在胃中占总消化物氮的约20%，在空肠中部增加到约80%（P<0.01），在盲肠中降低到30%（P<0.01），并在整个大肠中增加。累积表观消化率的计算表明，除十二指肠外，总消化物氮在整个消化道中都有净消失。日粮NDF-N在整个消化道中都有净消失。P-N的NDS-N部分在十二指肠、空肠和小结肠中消失，但在回肠、盲肠和大结肠中有净出现。十二指肠中有S-N的净出现，回肠和盲肠中有净消失。消化道下段氮分配的变化和氮浓度的降低表明，空肠、回肠、盲肠和小结肠是氮净吸收的主要部位，小结肠中吸收的大部分氮是由NDS-N转化为S-N提供的。