In addition to grass, cows eat grains, such as corn, and harvested forages, such as alfalfa and grass hay. This applies to cows in a cattle farming facility. Generally, cows prefer to eat vegetative gras, as their digestive system is more suited for grass compared to grains.
Studies indicate that grains have a negative effect on a cow's digestive system. The high starch content in grains reduces the pH of the cow's rumen for creating an acidic environment that microbes digesting grains can work in. This results in the reduction of the cow's forage digestibility. Though there is no negative impact on the cow's digestive system due to eating harvested forage, the feed is costly in the long run.