This study was conducted to observe the effect of fiber digestion enhancement and inhibition factors on fibrolytic bacterial colony growth and fiber digestion in the rumen fermentation environment. In order to promote the fiber digestion, 0.2% NaOH of rice straw was used as a substrate in rumen in vitro fermentation. A 0.1% methylcellulose (MC) was added rumen in vitro culture with untreated rice straw to inhibit fiber digestion. When in vitro culture was performed using untreated rice straw as a substrate, all substrate adherent colonies and rumen suspended colonies of Fibrobacter succinogenes, Ruminococcus flavefaciens and Ruminococcus albus showed an increasing growth as incubation time progressed; however there were significantly more substrate-adherent colonies than rumen fluid floating colonies at all incubation times (p<0.05). Fiber substrate digestibility in in vitro rumen fermentation was significantly higher 0.2% NaOH treated rice straw than untreated substrate (p<0.05). In addition, substrate-adherent colonies of fibrolytic bacteria were significantly more in the NaOH-treated group than in the untreated group for F. succinogenes, R. flavefaciens, and R. albus (p<0.05). When untreated rice straw was added to an in vitro culture, with or without 0.1% MC, to create a rumen environment for inhibiting fiber digestion, substrate digestibility was significantly suppressed compared to that in the untreated group (p<0.05). Additionally, substrate-adherent colonies were significantly fewer in the addition of MC than in the untreated control group for F. succinogenes, R. flavefaciens and R. albus (p<0.05). The results indicate that surface-adherent colonies of bacteria decomposing fiber substrate are far more than rumen fluid floating colonies in the rumen fermentation environment, and the environmental factors of rumen fermentation give same associative effect on the fibrinolytic function of fiber bacteria and its ecological communities.

This study was to research the relationships between rice straw degradation and changes of fibrolytic bacteria population during the in vitro rumen fermentation. Dry matter(DM) digestion of rice straw and population of fibrolytic bacteria were measured at the 0. 4, 8, 12 and 48 hours during the incubation. The populations of F. succinogenes. R. albus and R. flavefaciens were defined as log copy number of 16S rDNA by technical method of Quantitative real-time PCR. Total population of F. succinogenes, R. flavefaciens and R. albus was sum of bactera attached on rice straw and suspended in medium. It's population was increased with incubation, reached top level of 29.0 Log copy No at the 24 hour and then decreased. In the meantime, DM digestion of rice straw showed the higher increasement from the 8 hour to the 24 hour than from the 0 hour to the 8 hour, and then a slowdown in increasing trend of digestibility. Attachments of F. succinogenes, R. flavefaciens and R. albus were detected immediately after start of in vitro rumen incubation. At the same time, the colonized bacterial share were respectively 34.5%, 84.4% and 67.9% in total population. All of them was reached the highest colonized bacterial share above 94.7% at the 4 hour incubation. However population of attached bacteria was shown the highest level at the 12 hour or the 24 hour incubation. Kinetics of colonization were formed area of top speed from the 12 hour to the 24 hour and respectively reached 10.33, 9.28 및 8.30 Log copy No/h/g DM at the 24 hour by F. succinogenes, R. flavefaciens and R. albus. The kinetics of rice straw degradation was formed top level of 0.95% DM/h at the 24 hour. The present results gave clear evidence that degradation of rice straw was increased with the development of total fibrolytic bacteria in process of rumen fermentation. Also, their attachment was largely occurred immediately after insertion of rice straw, the colonized bacteria was actively proliferated, and then degradation of rice straw was maximized.