RESUMO
Rice hulls from Hungary, Colombia, and Cambodia were used for measuring with the nylon bag method the dry matter degradability in the rumen of sheep. After 48 h rumen incubation time the dry matter loss varied between 10.0 and 27.7%. The 48 h rumen dry matter loss of rice hulls from Hungary increased from 14.0 (untreated control) only to 17.9, 20.1, and 17.0% after chemical treatment with 2% NaOH, 4% CaO, and 4% urea, respectively. gamma-irradiation with doses of 0, 0.1, 0.25, 0.5, 1, and 2 MGy effected rumen dry matter losses of unground rice hulls from Hungary of 6.4, 14.5, 13.5, 21.3, 37.1, and 70.5%. The apparent digestibility of organic matter of untreated rice hulls from Hungary amounted to 19.2%, as found in tests with wethers. The main reasons of low digestibility and the negligible effect of chemical treatments are the high contents of lignin (ca. 15%) and silica (up to 23% of the dry matter). Therefore rice hulls are not suitable as feedstuff for ruminants.
