To examine the effects of urea and different protein source supplementation on cattle, 28 crossbred Brahman cattle were arranged in a 90-day feeding trial with 7 treatments and 4 replicates. The basal diet consisted of Hymenachne acutiglum grass (1% body weight, DM basic), rice straw (ad libiltum) and rice bran (1.5 kg/head/day). Treatment diets were U1 and U2 at 30 and 60 g urea/100 kg BW/day, respectively; soybean meal at 360 g (SBM1) and 720 (SBM2) g/head/day; blood and feather meal (50:50) at 360 g (BFM1) and 720 g/head/day (BFM2). Rumen fluid was collected for measurements of pH, NH₃-N and bateria enumeration and volatile fatty acid (VFA) analy Weight of cattle was taken at the beginning and the end of the experiment. It was shown that rumen pH was not affected by diets but NH₃-N content was higher in the U2 diet. Total bacteria were highest on the SBM2 ration. The supplementation of either soybean meal or blood plus feather meal resulted in improved weight gain. Addition of urea to the basal diet had a lesser effect on growth rate. Growth rate was positively related with molar proportion of propionate in the rumen VFA.

Keywords: bypass protein, cellulolytic bacteria, protein supplementation, weight gain