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Classifications of Gastrointestinal Tracts

Audio transcript; narrated by Annette Buyserie, Oregon State University

Gastrointestinal tracts of domestic species are classified based upon digestive anatomy and physiology and type of diet consumed and utilized.

The two classifications based on digestive physiology and anatomy are simple nonruminants or monogastrics and ruminants. Nonruminants have a simple one-chambered stomach. Ruminants have a more complex four-chambered stomach that allows them to digest and utilize fiber.

The three classifications based on the primary type of diet consumed and utilized are omnivores, herbivores, and carnivores. Omnivores consume both plant and animal tissue; herbivores consume primarily plant tissue; and carnivores consume primarily animal tissue.

Table 1.1 lists the classifications of various domestic species.
Table 1.1
Classifications of Gastrointestinal Tracts
Animal Classification
Poultry Nonruminant omnivores
Swine Nonruminant omnivores
Horses Nonruminant herbivores
Dogs Nonruminant carnivores
Cats Nonruminant carnivores
Cattle Ruminant herbivores
Sheep Ruminant herbivores
Goats Ruminant herbivores

Poultry are classified as nonruminant omnivores. Figure 1.1 illustrates the GI tract of poultry.

Figure 1.1 - Poultry GI tract

The unique characteristics of the avian GI tract are discussed later in this lecture, however note the location and size of the crop, the proventriculus, the gizzard, and the pair of ceca.

The GI tract of swine is illustrated in Figure 1.2. Swine are classified as nonruminant omnivores.

Figure 1.2 - Swine GI tract

Note the relatively small cecum, located post-gastric and post-absorptive. The GI tract of swine, compared to other domestic animals, most closely resembles the human GI tract.

Horses are nonruminant herbivores. Figure 1.3 illustrates the GI tract of the horse.

Figure 1.3 - Horse GI tract

Note the relatively large cecum that allows the horse to consume and digest high fiber feedstuffs.

Dogs and cats are both nonruminant carnivores. The GI tracts of both species are relatively simple.

Cattle, sheep, and goats are all ruminant herbivores. Figure 1.4 illustrates the GI tract of cattle.

Figure 1.4 - Ruminant GI tract

The unique characteristics of the ruminant animals will be discussed later in this lecture. However, note the location and size of the four-compartmented stomach; specifically, the reticulum, rumen, omasum, and abomasum.

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