The pig has a digestive system which is classified as monogastric or nonruminant. Humans also have this type of digestive system. They have one stomach (mono = one, gastric = stomach).The monogastric differs from that of a polygastric or ruminant digestive system found in cattle and sheep.These animals have one stomach broken into four compartments.he digestive tract of the pig has five main parts: the mouth, esophagus, stomach, and small and large intestines (Figure1). The following discussion explains how each part digests nutrients. Figure 1. The mouth is where food enters the digestive tract and where mechanical breakdown of food begins (Figure 2).