Rôle of the rumen ciliate protozoa

Six rumen-fistulated and defaunated wethers were fed twice daily a pelleted diet of barley and dehydrated lucern at a rate of 50 g dry matter/kg body weight °-!5. Two months later, the sheep were divided into three equal groups. Each group was then inoculated in the rumen with one of the following three genera of protozoa : Polyplastron multivesiculatum (P), Entodinium sp. (E), or lsotricha prostoma (I). After two months, each group was subdivided and inoculated with an additional genus to obtain two sheep for each P + E, P + I and E + I combination. After an additional two months, two sheep were inoculated with a mixture of several genera to restore them to a conventional state. At the end of each of the four two-month periods, the total digestibility of organic matter (OM), acid detergent fiber (ADF), nitrogen (N) and fermentation in the rumen were measured. The P + E genera combination could not be obtained because E disappeared when the sheep were inoculated with the P species. However, these two genera can coexist in a rumen containing at least four different genera of protozoa. OM and ADF digestibilities were improved mainly by inoculating the P genus and, to a lesser extent, the E genus, but the effect of I was negative. N digestibility tended to be higher after ciliate inoculation, compared to the defaunated state. Furthermore, the pH in inoculat-