The contents of different parts of the digestive tracts were used to determine the fragmentation process of ingesta in Mongolian gazelle (Procapra gutturosa).
Other additives work too, like fatty acids which reduce methane by lowering the carbohydrate content and reducing a specific parasite in the rumen known as protozoa.
Well the fungi are important, even though they make something like 5% of the living things in the rumen, they can breakdown specific bonds between the lignin inside the cellulose.