Dr. Colleen Lewis / March 6, 2017

I received a phone call from the front desk that a reporter from National Public Radio (NPR) was going to call after lunch to talk with one of the veterinarians about “magnetizing cattle for the upcoming tornado season.” My head was spinning about the oddity of the phase, “magnetizing cattle.” I pictured long lines of cattle waiting to enter a large magnetizing machine that would put a charge on each beast as metal starts dropping from the sky and sticking to their hairy hides with a clinking sound. I had every intention of convincing the reporter from NPR that veterinarians did no such thing. But alas, I thought a little bit about the simple process of dropping a magnet into a cow’s stomach. We do this all of the time. Could this be considered “magnetizing cattle?” I began to buy into the idea of this crazy headline.

ACT 1: The Magnet and The Delivery
Small in comparison to a 500 pound heifer or steer, a 3 inch, cylindrical magnet is loaded into a balling gun and dispensed into the esophagus. The calf just needs to swallow to facilitate the magnet’s decent into the first compartment of the stomach, the reticulum. There, the magnet sits; and waits; to attract a piece of metal. The weight of the magnet keeps it fairly stable in the reticulum as the smaller, lighter particles of feed get broken down and circulate into the rumen: the second compartment.

ACT 2: The Metal Wire and Other Pieces
Abattoir magnets are often covered in metal fines, wire pieces, small nuts, fragments of nails and remains of unrecognizable bits attached to them. Years ago, when hay was commonly baled with wire, it was all too common to see a hard-working magnet with a few short pieces of wire and bizarre rusted chunks attached to it. The magnet-metal aggregates remind me of the little pinch-pot pottery my kids used to bring home from kindergarten: lots of small pieces melded together to create a unique piece of art.

ACT 3: Tornado Season
A tornado will certainly throw a ton of metal pieces out into a pasture, but cows graze with quite a bit of discern. Each bite of pasture grass is met with the teeth and upper palate coming together. Metal will be rejected in most cases. So, if the grazing cows aren’t eating the metal, who is? The cattle that are being fed a total mixed ration (TMR) are more likely to ingest a piece of metal. A TMR is traditionally a ground up smorgasbord of a fiber, concentrates and protein mixed together to be delivered as a complete meal. Now our cows can bolt feed down; no teeth required. The wire is likely sourced from the hay, though it can appear from many sources. A baler should have an active magnet attached to it to prevent these metal pieces from getting picked up from the hay field and packed into a bale. Once the metal is inadvertently delivered via the hay into the TMR, it is less likely to be detected as a cow ingests it in a mouthful.

ACT 4: Hardware Disease = Bovine Traumatic Reticuloperitonitis
Hardware disease is caused by a piece of wire that migrates forward from the reticulum through the stomach wall, through the diaphragm, and even as far forward as into the pericardial sack that surrounds the heart. Inflammation and infection along the wire’s path can quickly lead to fatal septicemia, called bovine traumatic reticuloperitonitis. The implicated wire is usually two and a half to three inches long with a gentle bend.  

Hardware disease is a fascinating phenomenon that most commonly occurs in dairy cattle, followed by beef cattle and occasionally in llamas. The effects of a wire causing traumatic reticuloperitonitis or pericarditis can be prevented by dropping a magnet into the reticulum of all cattle prior to a year of age, especially those that will be fed a TMR. I am not REALLY suggesting to “magnetize your cattle for the upcoming tornado season." But I am suggesting that you place a magnet in yearlings because the nature of how we feed cattle is not without the risk of ingesting a wire that can cause potential damage. 

About the Author
Dr. Colleen Lewis is a 1996 graduate of Kansas State University, College of Veterinary Medicine. Her career has taken her to many places as a practice owner, consultant, embryologist, and mentor. She enjoys mixed animal practice, teaching, traveling, farming and high school sports with her husband, Andrew and their three boys.