Relationship between Bacteria and Ciliate Protozoa in the Sheep Rumen

Abstract

S U M M A R YTwo sheep were reared together and then kept on a standard diet over a period of 9 months. The rumen of one sheep contained a mixed population of ciliate protozoal species ; the other was initially unfaunated, then faunated with Entodinium caudatum and then with Entodinium and Polyplastron multivesiculatum. For each sheep diurnal and day-to-day variations in total concentration, and concentration of particular types, of bacteria, in viable counts of bacteria on non-selective and differential media and in concentrations of the different protozoal species, were determined. Measurements were also made of in vitro rates of fermentation, rumen pH and ammonia and volatile fatty-acid concentrations. The presence of protozoa decreased rumen bacterial concentrations and increased ammonia and volatile fatty-acid concentrations. However, these changes were not always completely clear-cut since the protozoa changed the patterns of diurnal variation not only of bacterial numbers but of some metabolic activities and metabolites and also altered the balance of bacterial types. These results are discussed in the context of interactions between bacteria and protozoa and between protozoal species. The main effects of faunation of the rumen seem to be caused by non-selective ingestion of small bacteria by the protozoa.

Effect of Defaunation on Ruminal Gas and VFA Production in vitro

“…In vivo total VFA concentration is often decreased by defaunation1-3,6). Defaunation decreases ruminal organic matter digestion and this decrease provokes a decline in total VFA production19, 21) This decrease is also explained, in part, by the disappearance of protozoal acid production. While bacterial population size is larger in defaunated rumen than in faunated rumen6,14.21-23) According to the observations of previously published reports, there was probably a larger bacterial population in defaunated rumen, although enumeration of bacteria was not done in this study.…”

Effect of defaunation on protein and fibre digestion in sheep fed on ammonia-treated straw-based diets with or without maize

“…(Coleman, 1986). A tentative explanation of this indirect enhancement of cellulolysis is that non-cellulolytic protozoa favour the growth of cellulolytic flora by: (1) restricting the development of amylolytic flora, as a result of the ingestion of starch granules by protozoa or the selective ingestion of amylolytic bacteria, or both, (Kurihara et al 1968(Kurihara et al , 1978 and by; (2) preventing pH drop due to utilization of lactic acid (Chamberlain et al 1983) and the slow utilization of readily fermentable substrates by protozoa. These are likely to be observed in conditions where animals receive concentrate feed.…”

Flow cytometric sorting, phylogenetic analysis and in situ detection of Oscillospira guillermondii, a large, morphologically conspicuous but uncultured ruminal bacterium

“…Warner (1966) investigated the relationship between grazing behaviour and changes in rumen microbial populations in sheep and found that the population of Oscillospira in the rumen fluctuated and the length of the trichome also changed depending upon the amount of feed consumed. Kurihara et al (1968) reported that total counts of Oscillospira in the sheep rumen tended to decrease in the presence of ciliates. Although the number of Oscillospira cells is relatively small compared with other bacterial cells, they may make a significant contribution to rumen fermentation because of their large biomass, roughly equivalent to that of ruminal ciliate protozoa (Clarke, 1979;Williams & Coleman, 1997).…”