FEEDING EFFECT OF RICE STRAW ON ENERGY CHARGE AND DIGESTION OF RUMEN MICROORGANISMS OF FATTENED CATTLE

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(1)The morphological of components of straw from 26 rice cultivars (Oryza sativa L.) and quantitative anatomical features were determined and related to dry matter digestibility of their botanical fractions. Ultraviolet absorption spectra of the leafbaldes from rice plant cultivated with or without silica application was also examined. A feeding trial with sheep was carried out to measure particle size reduction of rice straw in the rumen as silica was fertilized or not. The greater digestibility of rice straw was related to its higher culm content, and inherently greater digestibility of its culm faction which was associated with the proportion of occupied area of specific tissue cells. The ultraviolet absobance around 320 nm in epidermal and sclerenchymal cell walls of the leafblade was much lower for rice straw cultivated with silica application than that without silica application. This was in good agreement with much decreases of p-coumaric and ferulicacid esters in rice strawfert … More ilized with silica, which negatively affected microbial degradation of straw tissue walls. Silica application on rice cultivation also had a positive effect on particle size red uction of the straw in the rumen.(2)Digestive activity and adenylate energy charge in the rumen of sheep fed on the four diets, formulated by two types of roughages (rice and oat straws) and two levels of concentrates, were investigated and related to the physicochemical characteristics of rice and oat straws including particle size reduction, passage rate in the digestive tract and rumination behavior of sheep. Similar rumen degradability of fibrous materials was observed under the 25% and 75% rice strawdiets, while with the oat straw diets, the value was lower for the 25% straw diet than for the 75% straw diet. Greater bite sizes and rumiation time observed with the straw diets was attributed to higher pH values and probably to higher adenylate energy charge of the microorganisms in the rumen of sheep compared to those of the oat straw diets, especially under the 25% straw diet. Greater particle size reduction and passage rate in the digestive tract of sheep were also observed for rice straw. Less