Composition and volume of the rumen microbiota of sheep fed on grass silage with different sucrose, starch and cellulose supplements

A comparative study was made of the effect of different sucrose, starch and cellulose supplements and the effect of different silage preservatives on the quality and quantity of the rumen microbiota of sheep fed on grass silage. The levels of the carbohydrate supplements were 15 % and 30 % of the dry matter of the daily rations, representing 2 1/2 and 5 g/kg animal live weight per day. The silages were prepared with three different preservatives: 1) AIV I solution (25 % formic acid and 20 % hydrochloric acid), 2) formic acid and 3) Viher solution (26 %formic acid and 70 % formalin). The total number of ciliates was highest in the animals receiving sucrose with the silage, lower in those given starch and lowest in those given cellulose. On the pure silage diet, it was between those for the starch and cellulose diets. The total number of bacteria decreased in the opposite direction on the different diets. The sucrose supplements increased the numbers of small ciliates especially and the cellulose supplements those of the bigger ciliates. The total volume of the ciliate fauna was thus highest in the animals on cellulose diets, lower in those on starch diets and lowest in those on sucrose diets. The total microbe mass constituted the following percentages of the rumen content on the different diets: only silage 4.1, 15 % sucrose 3.5, 30 % sucrose 3.5, 15 % starch 4.0, 30 % starch 4.5, 15% cellulose 4.6 and 30 % cellulose 5.2. Bacteria constituted 77—86 % of the total microbe mass on the different diets, the precentage being highest on the sucrose diets and lowest on the cellulose diets. Only small differences were found between the different silage preservatives in the effect on the rumen microbiota