Nutrional and Physiological Study on Cecal Functions of Chickens

结果总结如下：(1)饲粮尿素在胃肠道不被降解，而是以完整的形式从空肠吸收。(2)被吸收的尿素不被水解，而是排泄到小管尿中。尿液中的尿素通过反蠕动作用从泄殖腔被带回盲肠，在那里被盲肠菌群水解成氨，并被盲肠壁吸收。(4)吸收的氨一部分在肝脏中用于合成非必需氨基酸，一部分以尿酸的形式通过谷氨酰胺的形成排出体外。(5)尿中其他含氮化合物也通过盲肠途径回收，并以与尿素相似的方式代谢。(6)该系统通过盲肠回收的氮在蛋白质匮乏的鸡体内得到有效利用，而在蛋白质充足的鸡体内利用率较低。(7)从肠道吸收中逸出的食糜进入盲肠对饲粮氮潴留产生不利影响。(8)鸡体内的氮潴留是基于食糜和尿液两种输入的平衡。(9)盲肠菌对营养不良的野禽的氮营养有有益作用，而对营养良好的鸡则没有作用。（10）盲肠结扎不影响饲粮的代谢能值。（11）盲肠菌群受食糜和尿液的进入、宿主周围环境和膳食纤维（如多酚和低聚糖）的调节。（12）饲粮中添加果胶可增加盲肠重量和面积。由此可见，鸡盲肠从蛋白质供应角度对氮代谢起重要作用，但对能量代谢不起作用，饲粮纤维通过盲肠发酵参与营养物质的利用。

The results are summarized as follows;(1) Dietary urea is not degraded at the gastro-intestinal tract, and absorbed in intact form from the jejunum. (2) The absorbed urea is not hydrolyzed but excreted into tubular urine. (3) The urinary urea is carried back from the cloaca into the ceca by antiperistalsis, hydrolyzed there to ammonia by cecal microflora and absorbed from the cecal wall. (4) A part of the absorbed ammonia is utilized for synthesis of non-essential amino acids in the liver and a part is excreted in the form of uric acid by way of glutamine formation. (5) Other urinary nitrogenous compounds are also recovered by the pathway through ceca and metabolized in a similar manner to urea. (6) The recovered nitrogen by this nitrogen recycling system through ceca is utilized effectively in the protein-depleted chicken but less utilized in the protein-adequate chickens. (7) The entry into the ceca of digesta escaped from intestinal absorption adversely exerts on dietary nitrogen retention.(8) Nitrogen retention in chickens is based on balance of two entries of digesta and urine. (9) Ceca beneficially function in nitrogen nutrition of wild birds under severe nutritional conditions but not in well-nourished chickens. (10) Cecal ligation does not affect metabolizable energy value of diets. (11) Cecal microflora is regulated by the entry of digesta and urine, ambient circumstances around hosts and dietary fiber such as polyphenol and oligosaccharide. (12) Dietary pectin increases cecal weight and area.It is concluded that the ceca of chickens play an important role in nitrogen metabolism according to protein supply, but not any role in energy metabolism, and that dietary fiber is involved in nutrient utilization through cecal fermentation.