Pigs and chickens are non-ruminant, monogastric animals that digest food in one stomach, similar to humans. They are fed grains that digest easily, such as soybean meal for protein and corn for energy.
Horses and rabbits are non-ruminant herbivores whose digestive tracts have mono and polygastric capabilities. The stomach and small intestine process starch, proteins, vitamins and minerals, but the fibrous part of their feed passes through the small intestine to the hindgut where fermentation further breaks down the food. Herbivores, such as zebras and rhinoceroses, expel large amounts of undigested food. To obtain necessary nutrients, they must continually graze and eat huge quantities of food.