The Effect Of Dietary Forage Quality On Rumen Microflora And Fiber Degradation In Sheep

Nine Inner Mongolian semi-fine wool sheep, fitted with permanent ruminal and proximal duodenum fistula, were used to study the effect of forage quality on rumen microflora and fiber degradation of sheep. The dietary ratio of concentrate to forage was 2:8. The animals were divided into three groups and fed three different diets respectively. The diets contained different quality of mixed forages according to Forage Grading Index. Three groups fed contained diets were named as HGI group,MGI group and LGI group. The results were as follow:â’ˆThe population of rumen microbes determined method showed that there was no significant differences among groups in the population of rumen bacteria,protozoa and cellulolytic bacteria(P>0.05), however the population of these microbes increased with the increase of dietary forage quality.â’‰The synthesized three species of ruminal cellulolytic bacteria (Ruminococcus flavefaciens, Ruminococcus albus, Fibrobacter succinogenes) and bacteria current probe marked with digoxin were applied to current experiments. The relative amounts of three ruminal predominant cellulolytic bacteria were determined by quantitative dot-blot hybridization using these oligonecleotide probes of 16S rRNA. The percentages of Fibrobacter succinogenes in solid digesta and liquid digesta were found in the highest among three major cellulolytic bacteria. With the dietary forage quality improved, the sum of three major cellulolytic bacteria and Fibrobacter succinogenes in solid phase and the relative amounts of the sum of three major cellulolytic bacteria and Ruminococcus flavefaciens in liquid phase were increased significantly (P<0.05). The relative amount of solid attached ruminal cellulolytic bacteria was significant higher than that of liquid attached ruminal cellulolytic bacteria.â’ŠThere were no significant differences among groups in the activities related to fiber degradation in the rumen liquid digesta(P>0.05). The activities of xylanase and pectic enzyme in rumen solid digesta had a increasely tendency with dietary forage quality improved. The differences of activity of xylanase in the rumen solid digesta among three groups reached at statistical significance (P<0.05). The activities related to fiber degradation in the rumen solid digesta were significant higher than the activities related to fiber degradation in the rumen liquid digesta.â’‹With dietary forage quality improved, ruminal pH value and concentration of propionate, butyric acid and BCP were increased, however oxidation-reduction potential value and ratio of acetate to propionate were declined with the improvement of dietary forage quality. With dietary forage quality improving, fiber digestibilities in the rumen and gastric area and fiber dynamic degradation coefficient were rised.