The Maxi Mag magnet is a powerful, high density, high-energy poly-coated ceramic cattle magnet with superior pulling power. When in the cow's stomach, metals on the magnet can be repositioned with minimum pressure on the reticular wall, reducing punctures. Give a magnet when they see early signs of possible hardware problems.
Cattle eat quickly, without sorting their feed. They often ingest foreign material, especially when eating hay or processed feed. The magnets are designed to sit in the cow’s rumen.
Foreign objects that don't pass through usually fall into the reticulum. Contractions of this stomach during normal digestion may push them through the stomach wall. The reticulum lies against the diaphragm.
Cows may ingest fence staples, barn nails, bits of wire or any other objects that find their way into the feed. Old fence wire lying in a field, with the hay grown up around it, may be chopped up by the swather and baler, ending up in hay. Nails, roofing tacks or other sharp metal objects are often found around a barnyard or a junk pile that cattle have access to when grazing. In feedlots, metal pieces may come off feed-handling equipment and be mixed with the feed.
And it sits there collecting stray metal before it can cause the cow pain. The magnet remains inside the cow for the life of the animal (and apparently can be reused afterward), and the presence of the magnet and the attracted metal in the rumen apparently has no effect on the cow’s health or lifespan. This magnet is sold by the each. If you want a full box there is 24 in a box.