Effect Of Yeast Culture On Rumen Fermentation And Application Of 16S RRNA Quantitative Analysis Technique

Four 500-600kg steers with rurainal cannula were used to study the effect of three kinds of yeast culture products on the rumen fermentation and bacterial population. The pH, concentration of NH:,-N and volatilisable fatty acids in the rumen were measured every two hours during trial. Activities of CMCase, Salicinase, xylanase and crystal cellulosase were analyzed by indirect colorimetry. The populations of three ruminal predominant cellulolytic bacteria (Ruminococcus flavefaciens, Ruminococcus albus and Bacteroides succinogenes) were determined by quantitative slit Northern blotting using oligonucleotide probes to 16s rRNA. The total counts of rumen bacteria were counted under light microscope.The results indicated that, when YC were added, the values of pH in the rumen were not altered significantly (p=0. 4051), but the concentrations of NH3~N at two-hour after feeding increased significantly (p<0.05). The average concentrations of acetate, propionate, butyrate and total VFA in the rumen of the catties with "YS" treatment increased significantly too (p<0.05), and the other groups with "DFM" and "XP" treatment gave a trend of increasing , not significantly, in the same thing. At the same time, the ratio of acetate to propionate decreased significantly with "DFM" and "YS" treatment (p<0.01), while "XP" treatment gave a trend of decreasing, not significantly. Treated with YC, the activities of three cellulolytic enzymes, CMCase, Salicinase and Xylanase, increased significantly (p<0.01), but the crystal cellulosase was not affected. There was a trend of increase of total bacteria count after addition of YC (p=0. 2363). Furthermore,inthe relative amount of R. flaveciens and sum of the relative populations of the three cellulolytic species increased significantly (p<0.01) with the YC treatments. Through the quantitative slit Northern blotting technique, the percentage of the relative population of the three cellulolytic species was 3. 80 +0.2% of the total bacteria population.There are two conclusions arose from the above. With YC treatment, the activities of three cellulolytic enzymes, CMCase, Salicinase and Xylanase, were increased, while the activity of crystal cellulosase weren't altered much. It gives a reasonable explanation to the result that YC increased the initial rate of forage digestion in the rumen without altering overall digestibility. The other, the quantitative analysis of the relative population of the three cellulolytic bacteria species with slit blotting technique using oligonecleotide probes to 16S rRNA gave a credible result, which is reported to be 0. 3% to 4%. It indicates such technique is reliable.