Like goats, cows are ruminants, which means their stomachs have four chambers, allowing them to chew, digest and regurgitate their food multiple times.
However, the process by which grass and fiber is broken up in the stomachs of cows and other grazing ruminants has a byproduct, methane, a potent greenhouse gas.
As ruminants with multi-chambered stomachs, bison can extract more nutrients from grass and this may help explain why they survived when other grazers such as the wild horses did not.