Cow magnets are primarily used to prevent hardware disease in cows. Hardware disease is caused by cows inadvertently eating metal like nails, staples and baling wire, and then the metal settles in the reticulum. The metal  can threaten the cow’s surrounding vital organs and cause irritation and inflammation in the stomach. The cow loses her appetite and decreases milk output (dairy cows) or her ability to gain weight (feeder stock). Cow magnets help prevent hardware disease by attracting stray metal from the folds and crevices of the rumen and reticulum. When properly administered, one cow magnet will last the cow’s lifetime. Alnico cow magnets are composed of aluminum, nickel and cobalt, and they sometimes contain copper and/or titanium.