Rice straw is abundant in Japan, for it is available as the by-product of rice. It has been used as part of roughages for a long time. Recently, the composition of rice straw would be changed by the improvement of breeding, cultivation and harvesting method of rice pant. In these days, flesh rice straw is increasing as the result of the development of threshing methods of rice in flesh condition and it receives considerable attention as the resources of roughages.
The object of this investigation is to make clear the chemical composition and the nutritive value of rice straw. The rice straw used for analysis were obtained from 219 samples which were collected in Aomori, Iwate, Akita and Yamagata Prefecture during 1967-1968.
The flesh rice straw shows greenish tint and has more leaves at the time of harvests and has higher crude protein content than usual dry rice straw. The percentage of crude protein content of the flesh rice straw was 3%-10%. The correlation coefficient of the content of crude protein and crude fiber was -0.22. The straight regression equation was represented by Ÿ =3.17 -0.39 (X-5.6) (Ÿ:percentage of crude fiber content X: percentage of crude protein content.) There was the tendency that the straw which contain higher crude protein was lower in crude fiber content.
Among the varieties of rice plants, Reimei and Fujiminori which are the varieties of stout, early grown and heavy head, had higher crude protein content.
As to the environmental factors such as soil and climate, cool upland districts, low lands with high moisture or the volcanic ash soil paddy fields seemed the causes of the high crude protein content of rice straw. The amount of applied fertilizer was also the influential factor which affects the crude protein content of rice straw.
From the results his investigation, it was recognized that recent development of fertilizing and harvesting methods are the causes to increased the nutritive value of rice straw at the time of harvests.