Postprandial variations in endogenous metabolic activities of ovine rumen ciliate protozoa

The effects of diet and of time after feeding on the endogenous metabolism of four different subfractions of rumen ciliate protozoa (mixed population, large entodiniomorphid, Isotricha and Dasytricha spp.) were examined, with respect to the production of gas, acetate, butyrate and l-lactate and rates of uptake of glucose. The type of feed, and time after feeding, had a marked effect on the composition of the sampled rumen protozoal population, with respect to metabolic activity of the component groups. The heterogeneity of these subpopulations, with respect to their relative metabolic activities at different times, are clearly demonstrated. The data are in general accord with related findings; e.g. protozoa from sugar-beet-fed animals were more active than those from hay-fed animals, and previous measurements of rumen dissolved gases agreed with the present measurements of activity within protozoa.