高蛋白質飼料給与山羊の消化管に出現する内因性尿素の量的考察

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An experinent was carried out with goats fed on a normal-and highprotein ration to clarify the quantitative relationship in the appearance of recycled urea in the digestive tract.The isotope-dilution method with 15N-urea and 15NH4C1 was used in this experiment.When the serum urea level was 172 mg N/l, the amount of urea transferred from the blood urea pool to the rumen ammonia pool was 0.9 mg N/kg, which was estimated to be approximately 23% of the total amount of urea having appeared in the ammonia pool of the digestive tract.When the serum urea level was 360 mg N/l, the corresponding amount of NH3 was 1.2 mg N/h/kg, which was estimated to be approximately 14% of this total amount.The amount of saliva secreted was measured directly by the oesophagel fistula method.The ratio, salivary secretion: diffusion through the rumen wall was calculated to be 2: 1 and 5: 1, when the serum urea level was 172 and 360 mg N/l respectively.In goats fed high-protein ration, the rumen was assumed to be replaced as the site of appearance of recycled urea by the lower part of digestive tract, and it was verified that the principal mode of transfer of blood urea to the rumen was the salivary secretion.
社団法人日本畜産学会の論文