Question

what is special about ruminant stomach how does it help the animal digest vegetable matter​

Answer 1

Plant material is initially taken into the Rumen, where it is processed mechanically and exposed to bacteria than can break down cellulose (foregut fermentation). The Reticulum allows the animal to regurgitate & reprocess particulate matter ("chew its cud").

Answer 2

Ruminants are mammals that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions. ... The process of rechewing the cud to further break down plant matter and stimulate digestion is called rumination.