NR 02. Effect of reducing the rumen ciliate protozoa population by feeding saponin-containing plants on rumen function of sheep fed on wheat straw

Grazing ruminants depend basically on the efficiency of rumen ecosystem to supply the animal with the protein and energy required for fulfilling the metabolic demands. Nitrogen recycling is a natural process occurring in the rumen which reduces the amount of microbial protein flowing to the duodenum. The present experiment was aimed at evaluating the effect of eliminating (Defaunated group) and reducing the ciliate population by means of using saponin-containing fruits (Michu, Sapindus saponaria) at two levels (Michu-2 group (2 g Michu/kg BW) and Michu-4 group (4 g Michu/kg BW)) on the rumen function of sheep. Results showed rumen ciliate population decreased as the level of saponin inclusion in the diet increased. Conversely, cellulolytic bacteria and rumen fungi increased both in Defaunated and Michu-2 groups. However, rate and extent of cell wall rumen degradability were not increased despite the larger fibrolytic microbial biomass. Saponins appears to have a weak acid reaction and therefore work as a buffer for the rumen pH. The level of saponins included in the present experiment did not affect dilution rate neither was the rumen volume affected by defaunation. Growth rate of defaunated animals and of those with ciliated population reduced was 11 % and 39 % faster than that of Control animals. The improved performance may be associated with a larger bacterial flow to the duodenum and a lower nitrogen recycling as suggested by the lower ammonia concentration in the rumen (33 % lower, P < .05)