A grazing cow will use her tongue to wrap around grass and pull it into her mouth. Saliva helps lubricate the food and provides a medium for bacteria to attach to food particles.
Cows regularly regurgitate a food bolus for rechewing. This is called rumination. The chewing and rumination processes increase the surface area, making the feed particles more accessible to the microbes in the rumen for digestion.
Food particles are digested in the rumen by a process of fermentation. Methane gas is produced, which is released through burping/eructation by the cow. If the gas is not released, the cow will become bloated and potentially die.
Image: © Marga van Hulzen.