Rumen metabolism of swamp buffaloes fed rice straw supplemented with cassava hay and urea.

The objectives of this experiment were to investigate effects of cassava hay (CH) and urea (U) supplementation on feed intake, digestibility, rumen fermentation, and microbial protein synthesis of swamp buffaloes fed on rice straw. Four rumen-fistulated swamp buffaloes, 365 ± 15.0 kg, were randomly assigned according to a 4 × 4 Latin square design to receive four dietary treatments: T1 = CH 400 g/head/day + U 0 g/head/day, T2 = CH + U 30 g/head/day, T3 = CH + U 60 g/head/day, and T4 = CH + U 90 g/head/day, respectively. Results revealed that feed intake was not affected while nutrient digestibilities were increased (P < 0.05) with increasing U level supplementation especially at 90 g/head/day. Ruminal pH and temperature were not altered by urea supplementation, whereas ammonia nitrogen (NH3-N) and blood urea nitrogen were increased with urea supplement (P < 0.05). In addition, total volatile fatty acid and butyric acid were similar among treatments, while propionic acid (C3) was increased by level of urea supplement (P < 0.05), but acetic acid (C2) and C2/C3 ratio were significantly decreased (P < 0.05). On the other hand, protozoal population and methane production were decreased by CH and urea supplement, while bacterial population particularly those of proteolytic, cellulolytic, and amylolytic bacteria and efficiency of microbial nitrogen synthesis were linearly increased (P < 0.05). Based on this experiment, it suggested that supplementation of urea and cassava hay for buffaloes fed rice straw improved rumen ecology and increased fermentation end products and microbial protein synthesis while reducing protozoal populations and methane production. Urea supplements of 60-90 g/head/day when fed with cassava hay are recommended for swamp buffaloes consuming rice straw.