Paengkoum, S., Wanapat, M., Wachirapakorn, C. and Nontaso, N. 2013. The Effect of Roughage and Urea Solution Infusion Levels on Ruminal NH3-N Concentration and Nutrient Digestibility in Beef Cattle and Swamp Buffaloes. Science, Engineering and Health Studies. 4, 1 (Mar. 2013), 47–55. DOI:https://doi.org/10.14456/sustj.2010.5.