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Ruminants have a ruminant stomach (rumen) in which the food is pre-digested. It is then choked up again, chewed and swallowed again, and then the actual digestion begins. Due to the ruminant stomach, the animals can digest cellulosic food such as grass. A community of bacteria, fungi and protozoa is found in the ruminant stomach for this purpose. The fungi and some bacteria are cellulose growers, other bacteria break down starch and lactic acid and the protozoa stimulate the growth of the bacteria. Cellulose can only be used optimally if all three partners occur together.
Explanation for children: Cows have a special stomach in which the eaten grass is pre-digested. This stomach contains microorganisms that help cows digest cellulose. Several microorganisms are involved in the degradation: Bacteria, fungi and protozoa. They form a very good team, only if all three work together, the cellulose is decomposed 100%. After predigestion, the cow chokes the grass up again, then the actual digestion begins.