A cow magnet is a veterinary medical device for the treatment or prevention of hardware disease in cattle.
Traditionally, cow magnets were strong alnico magnets about 1 cm by 8 cm (0.4 by 3.1 inches) in the shape of a smoothed rod, but today they are more commonly several ring-shaped ferrite magnets attached to a stainless-steel or plastic core, in the same shape as the single-piece original.
Newer designs to help increase effectiveness include a cage design, in which the magnet holds metal objects inside a protective plastic framework. Even newer designs include a stronger array of rare-earth magnets inside a stainless steel body that resembles the original alinco design.
A rancher or dairy farmer feeds a magnet to each calf at branding time; the magnet settles in the rumen or reticulum and remains there for the life of the animal.
Cow magnet insertion procedure:
The magnet is administered after fasting the cow for 18–24 hours. This is most effective if done to the entire herd before the age of one.
The cow magnet attracts such objects and prevents them from becoming lodged in the animal’s tissue. While the resultant mass of iron remains in the cow’s rumen as a pseudobezoar (an intentionally introduced bezoar), it does not cause the severe problems of hardware disease.
Cow magnets are widely available from veterinary, feed supply, and scientific supply sources.