The Effects Of High-Concengtrate Diet And Its Fermentation Products On The Growth And Fermentation Activity Of Ruminal Fungi

Rumen is a complex micro-ecosystem where bacteria, protozoa, anaerobic fungi andarchae are the major microorganism groups. Previous reports showed that species and thenumber of ruminal fungi were affected by diet. In the present study, effects of volatile fattyacid mix (VFA_m), lactate, or phosphate on ruminal fungi were investigated and thedifference between organic acids and inorganic acid (phosphate) was compared by in vitrofermentation. A further experiment was conducted to investigate the respective effects ofacetate, propionate, or butyrate on ruminal fungi. Finally, based on the studies in vitro, threegoats were gradually adapted to high-concentrate diet to investigate the effect of diet on thenumber of anaerobic ruminal fungi. This thesis was described in the following threesections.In the first section, effects of volatile fatty acid mix (VFA_m), lactate, or phosphate onanaerobic ruminal fungi were investigated by in vitro fermentation. Results showed that thenumber of anaerobic fungi was reduced significantly (P＜0.05), and the time when thenumber of anaerobic fungi reached maxima was delayed as compared to the control. Thecumulative gas production, the number of anaerobic ruminal fungi, dry matter loss, andCMCase activity decreased significantly when the value of pH was lower than 6.0 or theconcentrations of fermentation products were higher than 50mM (P＜0.05). It suggested thathigher concentration of lactate or VFA inhibited the proliferation of anaerobic ruminal fungiand reduced their fermentation activity. The inhibition of organic acids (lactate, VFA) wasstronger than inorganic acid under the same condition of pH and concentration.In the second section, the effects of acetate, propionate, or butyrate on ruminal fungi atfermentation in vitro were compared. The number of anaerobic ruminal fungi was reduced significantly (P＜0.01). No significant difference was detected between acetate, propionatetreatments and the. control in dry matter loss and cumulative gas production (P＞0.05).Carboxymethylcellulase activities in acetate and propionate treatments were higher than thecontrol, and positive relationships were observed between enzyme activity and cumulative gasproduction with coefficient as were 0.975 and 0.983 for acetate and propionate treatments,respectively. The enzyme activity decreased significantly when the value of pH was loweddown to 6.0 (P＜0.01), but the activity in the acetate treatment was still higher.than that intreatments of propionateor butyrate. Results showed that acetate, propionate, or butyrateinhibited the proliferation of anaerobic ruminal fungi. Acetic acid or acetate could be anunknown-factor that induced ruminal fungi to produce more carboxymethylcellulases.In. the third section, three goats with permanent rumen fistulae were gradually adaptedfrom an all-forage diet to a 70% concentrate diet inⅠ;Ⅱ,Ⅲ,Ⅳperiods to investigate theeffect of diet on anaerobic ruminal fungi. The number of ruminal fungi in periodⅡ(3:7)was the highest in the four (P＜0.01), and then decreased orderly in periodⅢ,Ⅳwith thevalues significantly lower than periodⅠ(P＜0.05). When the concentrate was fed, the.concentration of TVFA increased greatly (P＜0.05), and the concentration of lactate in therumen increased, but without accumulation (≤0.71 mmol, L^-1). The concentration ofpropionate had a strongest negative relationship with the number of ruminal fungi(r=-0.705). It suggested that the growth of ruminal fungi could be promoted by addingcertain ratio of concentrate in the diet of goats, but decreased sharply when the ratio wasover than 50%.