Animal Science: Digestive System Differences

Potbelly pig

The differences in digestive features between horse, cattle, and pigs comes down to compartments. There are four types of animal digestive systems: monogastric, avian, ruminants, and pseudo-ruminants (CAERT, Inc., 2016). For this question I am focusing on all of the above except avian.

A monogastric digestive system has one simple stomach. This is the type of system humans and pigs have. The monogastric system secretes acid in a low pH which allows the animal to break down feedstuffs high in energy and low in fiber like cereal grains (corn, wheat, barley, and oats) (CAERT, Inc., 2016). This is different than a cow, which would be considered a ruminant.

The ruminant system is composed of a large stomach that has four compartments inside it (Rowan, Durrance, Combs, & Fisher, 2015). The ruminant system is composed of the rumen where the food is mixed and a first pass at breaking it down occurs thanks to the millions of bacteria that live there. Then food passes to the reticulum where non-food stuff like rocks, nails, etc. are separated out. Ruminants do not chew their food like pigs and humans, so they sometimes swallow things they shouldn’t. The food then passes to the omasum where it is ground down and finally it goes into the abomasum, which is the same as in monogastric animals (CAERT, Inc., 2016). Feed-wise, “cattle and sheep can live on hay and pasture, while pigs must eat grains that can be digested more easily” (Rowan, Durrance, Combs, & Fisher, 2015). Although this allows for cattle to eat different pasturage than pigs, it also accounts for a “reduced feed efficiency compared to other livestock species such as poultry or swine” (Radunz, 2012). This is why cattle are seen constantly chewing their cud; the grass (for example) must be chewed to extract every nutrient possible. This is also why cows can get sick so easily, as the foreign material in their system and any imbalances in their bacteria can make them go off their feed or become ill and listless.

Finally we have the pseudo-ruminant, which is where horses fall. The horse is a non-ruminant because its stomach does not contain multiple compartments. Instead they have a simple stomach and a second stomach more like the rumen portion of a cow. These sections are called the foregut and hindgut. The foregut is where the feed is broken down by enzymes and the hindgut is where it is fermented  (Cubitt, 2010). Since the horse has similarities to both cattle and pigs, one may think that it needs to eat similar food, however, the unique digestive tract means that a horse’s diet also needs to be unique. Horses should eat good quality forage (hay, pasture, etc.). Abrupt changes in diet or adding too much grain to the diet can cause a build-up of lactic acid (Wright, 1999).

The differences in digestive systems accounts for the differences in feed. For horses and cattle, hay and pasture are most appropriate, although the quality of the feed needs to be higher in horses than for cattle. For pigs, corn, grains, oats, and barley are the most appropriate. Pigs and horses, like humans, can also get by with eating foods like apples and vegetables, where cows could not.

References

CAERT, Inc. (2016). Types of Animal Digestive Systems. Retrieved from Central Community School District 4: http://www.cusd4.org/vimages/shared/vnews/stories/4e679ba30e7a0/Types%20of%20Animal%20Digestive%20Systems.pdf

Cubitt, T. (2010, January 1). Health & Nutrition Articles. Retrieved from Hygain: http://www.hygain.com.au/horses-digestive-system/

Radunz, A. (2012, January 18). Back to Basics: Ruminant Digestive System. Retrieved from WI Beef Information Center: http://fyi.uwex.edu/wbic/2012/01/18/back-to-basics-ruminant-digestive-system/

Rowan, J., Durrance, K., Combs, G., & Fisher, L. (2015, August). The Digestive Tract of the Pig. Retrieved from University of Florida IFAS Extension EDIS: http://edis.ifas.ufl.edu/an012

Wright, B. (1999, September 1). Equine Digestive Tract Structure and Function. Retrieved from Ontario Ministry of Agriculture, Food, and Rural Affairs: http://www.omafra.gov.on.ca/english/livestock/horses/facts/info_digest.htm