Graminivore
In zoology, a graminivore (not to be confused with a granivore) is a herbivorous animal that feeds primarily on grass (specifically "true" grasses, plants of the family Poaceae). The word is derived from Latin "graminis", meaning "grass", and "vorare", meaning "to eat." Graminivory is a form of grazing. These herbivorous animals have digestive systems that are adapted to digest large amounts of cellulose, which is abundant in fibrous plant matter and more difficult to break down for many other animals. As such, they have specialized enzymes to aid in digestion and in some cases symbiotic bacteria that live in  their digestive track and "assist" with the digestive process through fermentation as the matter travels through the intestines. Horses, cattle, capybara, hippopotamuses, geese, and giant pandas are examples of vertebrate graminivores. Some carnivorous vertebrates, such as dogs and cats, are known to eat grass occasionally. Grass consumption in dogs can be a way to rid their intestinal tract of parasites that may be threatening to the carnivore's health. Various invertebrates also have graminivorous diets. Many grasshoppers, such as individuals from the family Acrididae, have diets consisting primarily of plants from the family Poaceae. Graminivores generally exhibit a preference on  which species of grass they choose to consume. For example, according to a study done on North American bison feeding on shortgrass plains in north-eastern Colorado, the cattle consumed a total of thirty-six different species of plant. Of that thirty-six, five grass species were favoured and consumed the most pervasively. The average consumption of these five species comprised about 80% of their diet. A few of these species include "Aristida longiseta", "Muhlenbergia" species, and "Bouteloua gracilis". References.