What is the function of bacteria that live in the digestive tracts of ruminants such as cows?

Answer 1

they break down cellulose to provide energy to the ruminant. Most of the ruminants energy comes from volitile fatty acids.
these bacteria are also a source of protein once they pass further down the GI tract. They make vitamins as well. Ruminants are wonderful.

Answer 2

They provide vitamin K as well some other useful materials for our body as well they protect our body from some dangerous bacteri