Now that my dairy judging mini-series has come to an end, it’s time for me to talk write about other dairy industry issues. One topic that you may or may not be familiar with is ruminology, or the study of the ruminant digestive system. If you already know something about ruminants, then most of this should be review, but if not, I hope that you learn something new!
Let’s start with the basics. Humans are considered to be monogastric when it comes to digestion, meaning that we are simple-stomached animals. Our stomach only has one compartment (“mono”) and contains hydrochloric acid (HCl) that breaks down our food. Some other animals, like dogs, cats, and pigs, also possess monogastric digestive systems, while other species have more complex digestive systems. Traditionally, these complex digestive systems are called ruminant digestive systems, which have four stomach compartments and allow the animal to digest plant material that cannot be digested by monogastrics.
Let’s take a tour of the ruminant stomach. The largest compartment of the ruminant stomach is the rumen. The rumen (pH of 6) is also called the “fermentation vat” because it contains millions of microbes (bacteria, fungi, and protozoa) that help to digest the contents of the rumen. The rumen also contains thousands of finger-like projections called papillae that help to increase the rumen’s surface area. A picture of rumen papillae is shown below:
Because the forages (plants) that ruminants consume are difficult to digest, cattle must regurgitate, rechew, and reswallow their food in order to maximize the nutritional uptake from feeds. This process is called “cud chewing” or ruminating. Cows can often be seen chewing their cud when they are calm or relaxed; a cow will ruminate for approximately eight hours per day. The ball of partially-digested food regurgitated during rumination is called a bolus (or cud).
As you might suspect, all of this microbial digestion in the rumen results in a lot of gas build-up inside the cow. Cows will become bloated if this gas is not released. The most common mode for gas release is belching (also called eructation). If that term made you smirk, just wait until you read the next one. The technical term for chewing is mastication. So now the next time you want to harass your friend, just make some comment about him/her masticating (it’s sure to get some sort of reaction)!
This cow is masticating or chewing her cud.
But back to business, the stomach compartment closest to the heart is called the reticulum. The reticulum is called the “honeycomb,” well, because it looks like a honeycomb. When cattle ruminate, the bolus passes through the reticulum before traveling back up through the esophagus. The reticulum is also very important in collecting foreign materials that cows may accidentally swallow. However, if a cow swallows something metal (like a nail), it could puncture the reticulum wall and potentially damage the heart and/or lungs, which could be fatal to a cow. This condition is called hardware disease. A magnet can be placed into a cow’s stomach to help prevent this condition.
Reticulum or “Honeycomb”
These are the type of magnets that could be given to a cow to prevent hardware disease.
The omasum is the stomach compartment responsible for water absorption. It is often called “many piles,” “many plies,” or “the Bible” because it contains numerous folds that give it more surface area.
Omasum
Finally, the abomasum (pH of 2),which is the largest stomach compartment in a newborn calf (about the size of a basketball), is often referred to as the “true stomach” because it contains hydrochloric acid and functions much like a monogastric stomach.
Abomasum
As usual, I could rant more about this topic, but I’ve already went over my word limit. I hope you learned something new. If you have any questions for me, ask them in the comment section and I will answer them for you!