The concentration of total VFA was not changed by the feed block and the mean values from 116.8 to 119.6 mmol/L. Foiklang et al. ( 2011 ) reported that VFA concentration in the rumen of buffalo fed with the feed block ranged from 102.2 to 116.0mmol/L. Supplementation of U-cas in feed block enhanced the proportion of propionic acid and deceased acetic acid concentration.