Study on the protein digestion and nitrogen metabolism of horses fed high-roughage diets

本研究以北海道本地马为研究对象，在回肠末端安装回肠管。1)饲粮蛋白质含量对马氮代谢的影响。随着蛋白质摄入量的增加，尿素在体内的合成和从体内向消化道的转移以及尿中尿素的排泄增加。当蛋白质摄入量减少时，从体内转移到消化道的氮大部分被用于尿素的再合成。这表明，当蛋白质摄入量减少时，尿素转移到消化道有助于马对尿素的利用。2)饲粮蛋白质含量对马饲料利用和后肠发酵的影响。粗蛋白质消化率和蛋白质积累率随蛋白质采食量的增加而增加。后肠总VFA和NH_3-N浓度升高，pH有降低的趋势。随着饲粮蛋白质水平的升高，小肠蛋白质消化率升高。然后，进入后肠的氮流量增加。NDF和ADF消化率以及尿中DAPA浓度不受饲粮蛋白质水平的影响。3)马回肠NH_3-N向血浆氨基酸的转移短句来源将标记为^<15>N的氨气注入回肠，研究内源性氨气进入消化道的命运。结肠中所有细菌氨基酸-n含有约1%的^<15> n -氮。血浆中游离必需氨基酸如亮氨酸、亮氨酸、亮氨酸、亮氨酸、亮氨酸、亮氨酸、亮氨酸均有较高的^<15>N。这表明血浆氨基酸的一部分来源于马结肠中细菌合成的氨基酸。

Hokkaido native horses fitted with the cannulae in the endo of ileum were used in this study.1) Effect of dietary protein contents on nitrogen metabolism of horses. Urea synthesis in the body and its transfer to digestive tract from the body, and urinary excretion of urea were increased with increasing protein intake. When protein intake was decreaed, most of nitrogen that transferred to digestive tract from the body were utilized for urea re-synthesis. This suggested that urea transfer to digestive tract made a contribution to urea utilization of horses, when protein intake was decreased.2) Effect of dietary protein contents on feed utilization and fermentation of hindgut of horses. Crude protein digestibility and the rate of protein accumulation was increased with increasing protein intake. Total VFA and NH_3-N concentrations in the hindgut was also increased, whereas pH tended to be decreased. When dietary protein level was increased, protein digestibility in the small intestine was increased. Then, nitrogen flow into the hindgut was increased. NDF and ADF digestibilities, as well as DAPA concentration in urine were not affected by dietary protein levels.3) Transfer into plasma amino acids from NH_3-N infused into the ileum of horses Ammonia labelled ^<15>N was infused into the ileum of hoses in order to investigate the fate of endogeneous ammonia translated into digestive tract. All bacterial amino acid-N in the colon contained about 1% of ^<15>N-nitrogen. Free essential amino acids in plasma, such as leu, ile, val, his, lys, phe, had higher ^<15>N. This suggested that a part of plasma amino acids originated from amino acids synthesized by bacteria in the colon of horses.