Influence of the presence of protozoa on the rumen microbial population of cattle.

Abstract

Three unfaunated cattle, fitted with a rumen fistula at the age of 9 months, were fed with hay wafer and pelleted concentrate. After two unfaunated cows were inoculated with a mixed population of protozoal species, changes of the bacterial populations as well as volatile fatty acids (VFA) and NH3 production in the rumen were followed for one month. The protozoal inoculum was prepared by using the rumen fluid obtained from a fistulated cattle given hay and concentrate ration. The third cow was kept protozoa-free as a control animal. A mixed population of protozoa established in the rumen of two cows within one month after inoculation. The number of total culturable anaerobic bacteria, amylolytic bacteria and cellulolytic bacteria decreased after the inoculation of protozoa. In contrast, the numbers of methanogenic bacteria, sulfate-reducing bacteria and anaerobic fungi increased after the inoculation of protozoa. The number of lactate utilizers decreased within 9 days after the inoculation of protozoa, and thereafter increased to the original level. Neither the number of xylanolytic bacteria nor pectinolytic bacteria changed after the inoculation of protozoa. The proportion of Ruminobacter amylophilus of total culturable bacterial population was reduced most significantly by the presence of protozoa, while that of Butyrivibrio spp., Selenomonas spp. and Clostridium spp. was increased. The NH3 and VFA production increased along with the proportion of butyrate after the inoculation of protozoa. The presence of protozoa affected markedly not only the number and constitution of bacterial populations, but also the NH3 and VFA production in the rumen.