In this study, sixteen Brahman cross-bred cattle were arranged in a completely randomized block design with four treatments and four replicates. The basal diet consisted of Hymenachne acutiglum grass, rice straw and rice bran (1.5 kg/head/d). Compared treatments were protein sources such as urea (120 g/head/d), soybean meal (720 g/head/d) and 50% blood meal and 50% feather meal mixture (720 g/head/d). Real-time PCR was applied to enumerate the presence of cellulolytic bacteria including Fibrobacter succinogenes, Ruminococcus albus and Ruminococcus flavefaciens and methanogens. It was shown that number of total bacteria, R. albus and R. flavefaciens remained unchanged over 90-day supplementation. However, F. succinogenes was influenced by the addition of urea and soybean meal with an increase of number at the end of the trial (P