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 improve 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).