牧草蛋白質の栄養価 : III．オーチャードグラスの乾燥時における窒素形態の変化

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In order to study the effect of various drying conditions upon the properteis of proteins in the grass, changes in nitrogen distribution in orchard grass (Dactylis glomerata) were observed.The drying methods adopted were (1) rapid heating(70°C for 2 hours with aeration), gradual heating (temperature was raised gradually to 70°C, which was maintained for 2 hours with aeration), and wilting (18-29°C for 3 days), and (2) drying with aeration (50-55°Cfor 3-4 hours), drying without aeration (50-55°C for 7 hours), and drying in the sun (for 3 days). The change of nitrogen distribution in the course of wilting was also examined for 7 days after cutting.Samples were extracted successively with water, 10% NaCl, 70% ethanol, 0.3% NaOH and hot 0.3% alkaline 60% ethanol. Total N and protein N (by the trichloroacetic acid method) were determined in each fraction.Results obtained are as follows.1) Total N contents in samples were not changed under any drying conditions. Protein N decreased remarkably after wilting, but hardly changed under the other drying conditions (Table 1).2)In the case of drying at 70°or 50-55°C, water-soluble protein N decrased, but hot-alkaline-ethanol-soluble protein N increased. The changes of NaCl-soluble protein N and ethanolsoluble protein N, both of which were contained in fresh grass in a very small quantity, were very small, although both components seemed to be decreased by drying. NaOH-soluble protein N, which was contained not so much in fresh grass, increased in some cases, but hardly changed in others. Any definite tendency was not observed in the change of insoluble N.Wilting caused a decrease in hot-alkaline-ethanol-soluble protein N as well as in water-soluble protein N. The effect of sun-drying upon the protein N distribution differed in one specimen from another (Table 3).3) Water-soluble non-protein N was increased distinctly under all drying conditions, espedally wilting. After drying at 70° or 50-55°C, NaCl-soluble non-protein N decreased considerably. Changes in non-protein N in any other fraction were not uniform among samples (Table 4).4) The changes in nitrogen distribution of grasses cut at different growth stages were not similar even under the same drying condition. Besides, the difference In effect upon the nitrogen distribution between various drying methods at 70° or 50-55°C was not clear.5) In the course of wilting, water-soluble protein N and hot-alkaline-ethanol-soluble protein N decreased rapidly and, accordingly, water-soluble non-protein N increased. This suggests that these major proteins autolyzed to yield water-soluble non-protein nitrogenous compounds (Fig. 1).
社団法人日本畜産学会の論文

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大山嘉信
関東東山農業試験場畜産部

牧草蛋白質の栄養価 : III．オーチャードグラスの乾燥時における窒素形態の変化

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