Rumen adaptation of swamp buffaloes (Bubalus bubalis) by high level of urea supplementation when fed on rice straw-based diet.

Four rumen-fistulated swamp buffaloes (Bubalus bubalis) were randomly allocated to investigate rumen adaptation of urea on feed intake, nutrient digestibility, fermentation efficiency, and microbial protein synthesis. Buffaloes were fed with rice straw ad libitum for a period of 2 weeks and then were shifted to a step-up diet regimen by supplementation of concentrate containing 20 and 40 g/kg urea at 5 g/kg BW for a period of 2 and 4 weeks, respectively. The results revealed that feed intake and nutrient digestibility were increased by urea supplementation (P < 0.05) both at two and four period of consumption. However, ruminal pH, temperature, and protozoal population were neither affected by urea nor adaptation period (P > 0.05) while bacterial and fungal zoospores were increased especially at 40 g/kg urea. Data from real-time PCR further showed that total bacteria and the three predominant cellulolytic bacteria (Ruminococcus albus, Fibrobacter succinogenes, Ruminococcus flavefaciens) were increased by urea supplementation both at 2 and 4 weeks of urea feeding. Furthermore, methane production was similar among treatments while microbial protein synthesis was enhanced when buffaloes were fed with urea after a period of 2 weeks especially at 40 g/kg urea (P < 0.05). It can be concluded that urea supplementation could increase feed intake, nutrient digestibility, microbial protein synthesis, and fermentation efficiency of swamp buffaloes fed on rice straw. It is suggested that buffaloes could adapt well and utilize urea as a N source effectively within a period of 2 weeks uptake without adverse effect.