Abstract: A real-time polymerase chain reaction approach was used in this study to determine the population of major ruminal bacterial species (Fibrobacter succinogenes, Ruminococcus albus, and Ruminococcus flavefaciens) in digesta and rumen fluid of swamp buffalo (Bubalus bubalis). Four rumen-fistulated, male swamp buffalo were randomly assigned according to a 4 x 4 Latin square design to evaluate the effect of the urea-treated rice straw (roughage source)-to-concentrate ratio on cellulolytic bacterial distribution. Animals were fed roughage-to-concentrate (R:C) ratios of 100:0, 75:25, 50:50, and 25:75, respectively. At the end of each period, rumen fluid and digesta were collected at 0 h and 4 h post-morning-feeding. It was found that feeding urea-treated rice straw solely increased these three cellulolytic bacteria numbers up to 2.65 x 10(9) and 3.54 x 10(9) copies per milliliter for F. succinogenes, 5.10 x 10(7) and 7.40 x 10(7) copies per milliliter for R. flavefaciens, and 4.00 x 10(6) and 6.00 x 10(6) copies per milliliter for R. albus in rumen fluid and digesta, respectively. The distribution of the three cellulolytic bacteria species in digesta were highest at 3.21 x 10(9), 4.55 x 10(7), and 4.56 x 10(6) copies per milliliter for F. succinogenes, R. flavefaciens, and R. albus, respectively. Moreover, at 4 h post-morning-feeding, the populations of the three cellulolytic bacteria were higher than found at 0 h post-morning-feeding. It is most notable that F. succinogenes were the highest in population in the rumen of swamp buffalo and cellulolytic bacteria mostly adhered to feed digesta in the rumen.

Abstract: This experiment was conducted to investigate the effect of lemongrass [Cymbopogon citratus (DC.) Stapf.] powder (LGP) on rumen ecology, rumen microorganisms, and digestibility of nutrients. Four ruminally fistulated crossbred (Brahman native) beef cattle were randomly assigned according to a 4 x 4 Latin square design. The dietary treatments were LGP supplementation at 0, 100, 200, and 300 g/d with urea-treated rice straw (5%) fed to allow ad libitum intake. Digestibilities of DM, ether extract, and NDF were significantly different among treatments and were greatest at 100 g/d of supplementation. However, digestibility of CP was decreased with LGP supplementation (P < 0.05), whereas ruminal NH(3)-N and plasma urea N were decreased with incremental additions of LGP (P < 0.05). Ruminal VFA concentrations were similar among supplementation concentrations (P > 0.05). Total viable bacteria, amylolytic bacteria, and cellulolytic bacteria were significantly different among treatments and were greatest at 100 g/d of supplementation (4.7 x 10(9), 1.7 x 10(7), and 2.0 x 10(9) cfu/mL, respectively). Protozoal populations were significantly decreased by LGP supplementation. In addition, efficiency of rumen microbial N synthesis based on OM truly digested in the rumen was enriched by LGP supplementation, especially at 100 g/d (34.2 g of N/kg of OM truly digested in the rumen). Based on this study, it could be concluded that supplementation of LGP at 100 g/d improved digestibilities of nutrients, rumen microbial population, and microbial protein synthesis efficiency, thus improving rumen ecology in beef cattle.