These results were in agreement with Cherdthong et al. (2011a) who reported that supplementation of U-cas as a slow release NPN source in concentrate diet which resulted in improveed digestibility and microbial mass in an in vitro experiment. Furthermore, the digestibility of aNDF and cellulolytic bacterial population were enhanced when dairy cows or beef cattle were fed with U-cas (Cherdthong et al., 2011b,c). In addition, a polymer-coated slow reduced urea was demonstrated to increase total tract DM and CP digestibilities in lactating dairy cows (Galo et al., 2003).