How can one understand the digestive system of a cow without knowing exactly how many teeth she has? A simple number can give us a better understanding of digestion, if we know a bit more about these teeth. Cows have 32 teeth, just like humans do. What is interesting is where these 32 teeth are distributed and why. We all understand the functions of our own teeth, front teeth are for biting and back teeth are for chewing, but what does a cow do since she has no upper front teeth?



A cow’s teeth are distributed much differently than a humans’ teeth are. Unlike humans, cattle can be born with or without teeth. When they obtain their permanent teeth, after 30 months, they have 12 premolars top and bottom, 12 molars on top and bottom, and only 8 incisors which are all found on the bottom of their mouths. Instead of upper incisors, a cow has what is called a dental pad, a patch of tough skin covering their gums.

At first glance it would seem that missing front teeth would be rather inefficient when it comes to eating, especially since cows can eat up to 100 pounds of grass per day. But the cow’s mouth is only one of the many parts of the digestive system. A cow’s stomach is separated into four different compartments, the first of which is the rumen. The rumen helps compensate for front teeth in digestion, further reducing the size of food particles.

When cows eat, they use their tongues to wrap around grass and their lower incisors to cut it. They swallow grass mostly unchewed. The swallowed grass will enter the rumen for a short time but then it is pushed back up through the esophagus and into the mouth, where it is chewed and re-chewed. This process, called cud chewing, is repeated for 6 to 8 hours. While the food bolus, or cud, sits in the rumen, the fibre is being broken down by resident bacteria and protozoa into fatty acids and absorbed through the rumen walls. The process of chewing cud and breakdown in the rumen decreases the particle size of the grass, making the chopping function of front teeth unnecessary. If you happen to see a cow in the pasture seemingly chewing on nothing, it is actually chewing on its cud.

Cattle aren’t the only ones that have a dental pad in place of upper incisors; most ruminants share the same dentition. Sheep, goats, deer, and even camel have teeth which are similar because they are ruminants and their rumen works to perform the function of upper incisors. Horses, on the other hand, are monogastrics, meaning they do not have a compartmental stomach and rumen. It is only logical then that horses don’t share the same dentition – they have upper incisors. By looking at an animal's mouth, you can tell what kind of stomach it has. Animals with no upper incisors can be assumed to be ruminants.

We can expect that if we brush our teeth twice a day we’ll be able to keep our 32 teeth until the day we die. Cows, however, can find themselves without teeth after only 10 years of age, a condition known as peg teeth. Normally cows do not reach the stage where they develop peg teeth as they are sent to market well before then. Although, as Dr. Reza Khorasani, the manager of the University of Alberta Dairy Research and Technology Centre explains, “[they] do see wear occurring on the teeth of [their] cattle.

Due to the large amounts of chewing a cow does, approximately 40 to 60 thousand jaw movements a day, their teeth are continually wearing down. This wear is consistent with most cattle and can be used to determine their age. However, according to Dr. Craig Wilkinson, a veterinarian and Director of Animal Care at the University of Alberta,

“After two years [teeth aging] becomes a very rough estimate [of age.]” Cows' mouths are not particularly prone to problems beyond terminal wear although Dr. Wilkinson points out, “They also occasionally get other problems such as broken teeth, or abscesses ... when cattle develop dental problems they are most often culled, then diagnosed.”

Although cows and humans may share the same number of teeth, their mouths have little else in common. Teeth placement and function are related to the digestive system of an animal. The cow’s compartmental stomach, specifically the rumen, takes the place of upper teeth. Don’t be alarmed if the next cow you see is apparently missing its front teeth or is chewing nothing for hours on end; she is just doing what all ruminants do best with what they have.

- Tyson, Bieleny, Sara Dargis, Kari-Ann Roveredo and Liz Simpson