Recycling of plants by-products and crop residues to be used asanimal feed will decrease costs of animal feeding and decrease theenvironmental pollution. Therefore the use of these low qualityroughages as rice straw in making silage as a preservation method ofgreen fodder or by their chemical treatment improve there nutritivevalue, also as a key for solving some of problems of environmentalpollution through its burring and animal feed shortage during summerseason.Experiment IThis Experiment was carried out to study the effect of feedingof sheep on diet contained 4% urea-treated rice straw with or withoutaddition of 5% molasses on chemical composition, feed intake,nutrient digestibility , rumen fermentation parameters and some serumbiochemical parameters.About 100 kg of 4% urea-treated rice straw was prepared andkept for 21 days. Another 100 kg of 4% urea-treated rice straw wasprepared with addition of 5% molasses. Six healthy Baladi rams (oneyearold) of nearly similar average body weight of 30 kg ±). They wereallotted into 3 equal groups (2 rams per each group), each group washoused separately in shaded pen (4*4 meter). Three experimental dietswere formulated to contain 60% concentrate mixture and 40%roughage. In the first diet (control) berseem hay used as the bulkyfeedstuff, while 4% urea-treated rice straw and 4% urea-treated ricestraw with 5% molasses were used to replace berseem hay in theSummary162second and third diet, respectively. Three digestibility trails werecarried out to determine the feeding value of experimental diets. At theend of experimental period rumen fluid sample were taken at 0 hourbefore feeding, 3 and 6 hours post feeding for 2 successive days formeasurement of ruminal pH and ammonia nitrogen and total volatilefatty acids concentrations. At end of each digestibility trail bloodsamples were collected.The obtained results revealed that:Changes in chemical composition: the results revealed an increase inCP content from 5% to 7.85% and 9.78% respectively and decrease inEE, ash, CF, NDF, ADF and NFE content for rice straw treated with4% urea or rice straw treated with 4% urea and 5% molasses.Average daily feed intake of roughage: the results revealed asignificant (P < 0.05) lower value in sheep fed diet contained 4% ureatreatedrice straw as compared to those fed diets contained either 4%urea-treated rice straw with addition of 5% molasses or the control. Ingeneral the treatment improved feed intake of rice straw.Nutrient digestibility of the diets: the results revealed that digestioncoefficient of DM and NFE didn’t show any significant (P > 0.05)difference in sheep fed diet contained 4% urea-treated rice straw, whiledigestibility coefficient for DM and NFE in those fed diet contained4% urea-treated rice straw with addition of 5% molasses wassignificantly (P < 0.05) higher as compared to that of the control diet.Ether extract digestibility of the diets contained either 4% urea-treated163