Cow magnet ingestion in livestock

Aside during the ball-identification exercise — Tom uses 400-series stainless steel cow magnets as the magnet props. Explains the livestock-medicine origin.

Do you know what a cow magnet is? It's a stainless steel magnet — made out of 400-series stainless. You stuff it in a cow's mouth and make them swallow it. It goes into the cow's belly because cows tend to eat a lot of scrap metal, and the scrap metal can tear up their intestines. If you have something that holds the metal in the belly, the hydrochloric acid in the stomach will digest the steel before it gets to the intestines. So dairy cows get to eat a magnet. They're called cow magnets, they're cheap, they're stainless steel, and they don't rust. So I bought a couple. Don't worry — they've never been in a cow.

Physical demonstration. Stainless-steel magnet swallowed by dairy cattle to capture stray ferrous wire and protect the udders. Used as an aside off the guide-wire topic.

[Tom produces a magnet.] It's a stainless steel magnet. None of you grew up on a farm, I take it. This is a cow magnet. You make the dairy cattle swallow this. It turns out, when they're out grazing, they sometimes pick up wire from the fence. If that gets into their udders, it destroys them, and they're not much good as a milk cow at that point. So the stainless steel magnet grabs onto the carbon steel that they might eat and holds it in the stomach. The stainless steel doesn't corrode in stomach acid, but the carbon steel sticks to the magnet and stays put.

Stainless-steel magnet swallowed by cattle to capture ingested metal in the stomach.

[Tom produces an Alnico magnet and a welding electrode.] This is an Alnico magnet. I have a piece of steel here, a welding electrode — I'll pass around the welding electrode and you can feel how strong it is. [Tom produces a cow magnet.] If I know what this shape magnet is — you can buy these off Amazon — it's a cow magnet. Anybody know why you call it a cow magnet? You put it in a cow's mouth and hold her mouth closed and she will swallow it. You want it in the cow's stomach, because cows will go out and graze and eat old tin cans and things like that, and that goes in and destroys their stomach and their intestines. But if you have a stainless steel magnet that will not dissolve in their stomach — the hydrochloric acid in their stomach will dissolve a steel can — cows eat steel, not intentionally, but it's not good for them. [Tom passes a neodymium-iron-boron magnet around.] This is a neodymium-iron-boron magnet, and it has about eight times the strength. Try to slide these apart if you want.