Bibliography: leaves 102-114. This study evaluates the difference in the nutritive value of rice straw varieties using chemical composition and digestibility measurements. It assesses several methods for improving the nutritive value of rice straw and the effect of urea treatment and rice straw quality on the colonisation of ruminal fungi and the characteristics of stem tissue structure.

Thesis (Ph. D.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 52-64). Also available on the World Wide Web.

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The effect of treatment with 3% aqueous ammonia and 5.3% urea plus jackbean meal on the nutritive value of wheat straw was investigated. The moisture content of the straw was raised to 40% by addition of water. Crude protein and in vitro dry matter digestibility were highest for the bottom layers, which had the highest moisture. The mean temperature during the first 4 wk post treatment was 11.2 C. Four diets were fed to sheep: untreated straw 1) alone or 2) with 20 g/d urea at feeding time 3) ammonia-treated straw, and 4) urea-treated straw. All diets contained 80 g of liquid molasses, 10 g of NaCl and 6 g of Na 2 S04, and were calculated to be isonitrogenous except the control diet (untreated straw without urea supplementation). Straw was chopped prior to feeding. Crude protein content in wheat straw was tripled by ammonia and urea treatment. Dry matter digestibility in vivo and in vitro was enhanced by ammonia and urea treatment, and the effect was higher for ammonia treatment. Digestibilities of cell wall constituents were higher (P<.05) for ammonia treated straw, compared to urea-treated straw. Urinary N excretion was considerably lower (P<.01) and N retention was higher (P<.01) for lambs fed treated straws, compared to those fed urea at feeding time. Ruminal NH3-N and blood urea concentrations were higher (P<.01) for the lambs fed urea at feeding time, compared to lambs fed the others diets. / M.S.

An experiment involving three feeding trials was conducted to study the effect of substituting chopped wheat straw for alfalfa in diets for lactating dairy cows. The results of these trials have shown that in complete mixed diets or diets containing long alfalfa hay, replacement of half of the alfalfa in rations containing 45% roughage for lactating dairy cows with chopped wheat straw does not adversely affect DM intake or milk yield and increase milk fat percentage. Replacing half of the long alfalfa with chopped alfalfa also apparently improved lactational performance although not as dramatically as that of chopped straw. Ammoniation of wheat straw did not improve the performance response by lactating cows. Inclusion of chopped straw in the diets seemed to enhance the efficiency of milk production. Higher ruminal acetate:propionate ratios and increased digestibility of ether extract resulted from feeding straw. Digestibility of other nutrients were generally either not affected or were depressed by straw feeding. Increasing the chopped wheat straw level to 75% of the roughage resulted in lower DM intake and milk yield and negative body weight gains but higher milk fat levels. It did not appear that maintenance of constant ADF level in a dairy ration regardless of roughage level was the solution to the maintenance of milk fat levels. Thus it has been indicated that under the conditions of this experiment a combination of chopped alfalfa and wheat straw can be used successfully in complete mixed rations for high producing dairy cows. For the most part all productive parameters measured were improved by the addition of straw and by the feeding of complete mixed diets. This was especially true for milk fat which, from a dairyman's viewpoint, is very important because of its impact on milk pricing. It would also have a direct bearing on management by reducing labor costs through elimination of labor intensive handling of long alfalfa. Mechanical handling of complete mixed rations is relatively easier and cheaper.

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