| This thesis reports a series of experiments designed to test the role ofrumen anaerobic fungi and enteractions among fungi, bacteria and protozoa inthe degradation of fibre.1. Effect of elimination of all anaerobic fungi on fermentation parameters,fibre degradation and outflow speed in rumen. Three Mongolian and han cross-bred rams (30±1.82 kg live weight )with a permanent cannula in the rumen and at the proximal duodenumrespectively were used to investigate the effect of elimination of anaerobic fungion fermentation parameters, outflow speed and fibre digestibility with nylon bagmethods in sacco.The results showed that the degradation rates of NDF, ADFwere significantly decreased (p<0.05) and degradation dynamics of differentnutrients were also changed. Concentration of NH3-N, TVFA and acetate wassignificantly decreased, however, the protozoa total numbers, the pH value, themicrobial protein synthesis and propionic concentration increased respectively(P<0.05). The results also showed outflow speed of fibre in rumen was significantlydecreased (p<0.05), however, the outflow speed of fibre in duodenum and ileumhave no difference (p>0.05). Except for HC, the flow of DM, NDF, ADF wasgreatly increased (p<0.05), and their digestibility was significantly decreased(p<0.05).2. Interaction among three different microbial populations in rumen 5 experiments were conducted to evaluate the interaction of fungi, bacteriaand protozoa by batch culture. Rumen fluid came from four local sheep fittedwith permanent cannula. Using chemical agent eliminated one or two kinds ofmicrobial among the three populations to get 7 culture systems. Those werebacteria (B), fungus (F), protozoa (P), three populations (X) and bacteria andprotozoa (BP), bacteria and fungus (BF), protozoa and fungus (PF) culturesystems, respectively. The results showed that elimination of anaerobic fungisignificantly increased the count of total protozoa and bacteria (p<0.05),elimination of protozoa significantly decreased the count of total anaerobicfungi (p<0.05), but the count of total bacteria went up, and elimination ofbacteria significantly decreased the count of total protozoa (p<0.05), while theproportion of Isotricha and Ophryoscolex greatly increased, in the meantime,the count of total bacteria also had a ascend trend. These results indicatedcoculture between bacteria and fungi existed antagonism, while in othercoculture fungi more depended on the protozoa population, the protozoa moredepended on the bacterial population. The degradation rate of fibre in three populations mixture culture washighest among all the cultures, and it was significantly higher in BP coculturethan single culture, while that was reduced in BF coculture than bacteriamonoculture.Gas production was highest in BP coculture, CMCase activity washighest in PF coculture, while the highest degradation rate was in X culture.These results showed the interactions between gas production or CMCaseactivity and the degradation rate of fibre were not always linear correlation fordifferent microorganisms' culture system. It seems that the fermentation activity was lower in monoculture or twopopulations than in three populations mixture culture. Concentration of NH3-N,microbial protein and pH valve displayed different order to 7 groups. Theseresults suggest different microbial population had different diversity andmetabolic mechanism.3. Conclusions The main conclusions of the experiments in this thesis are: 1. Rumen anaerobic fungi played important role in the degradation of fibre. 2. Three populations mixture culture was better than single culture or two populations coculture. 3. interactions between gas production or CMCase activity and the degradation rate of fibre were not always linear correlation...
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