Studies on the Defaunation of the Ovine Rumen Using Dioctyl Sodium Sulphosuccinate

The lethal concentrations of dioctyl sodium Sulphosuccinate (DSS) to nine species of rumen ciliate protozoa were determined. The quantity of DSS required to remove these protozoa from the rumen of sheep was approximately 30 times the lethal concentration. This was caused by interaction of the DSS with rumen particulate material, and the protozoa were killed only after the particulate fraction was saturated with DSS. Defaunation was conducted most efficiently after withdrawal of food for 24 h followed by a period (1–4 d) of reduced food intake by the host animal. In toxic concentrations of DSS the cilia of both holotrich and entodiniomorphid protozoa became detached, followed by leakage of the cell contents via the gullet or anus (in the entodiniomorphids) or at variable points in the cell wall (in the holotrichs). The population densities of most of the other rumen micro-organisms examined decreased during defaunation, but regained their original population density within 11–21 d. After this time the population densities of these organisms exceeded that shown before defaunation, with the exception of Oscillospira guilliermondii which was eliminated.