Premarin is a very common drug prescribed to millions of women worldwide as a hormone replacement therapy. The name stands for PREgant MAres uRINe, as the drug is produced from the hormones present in the mare's urine. The horses used to produce this drug are referred to as "PMU" horses, for short.
Premarin is created by collecting the urine of pregnant mares. The mares are kept in small standing stalls in order to limit their movement, so not to displace the urinary bladder bags used to collect every drop of urine. The mares are kept in this manner for a lengthy portion of their pregnancy, normally about six months. Once the mares are full term and ready to deliver, they are turned out to have their foals. The mares are able to nurse their foals until weaning age, about 4 months, at which time they are separated and the mare is bred back to repeat the whole process again. This cycle of breeding has created an overabundance of unwanted foals, most of which are sold to the slaughter industry. "PMU" farms exist all across the USA, and are also prevalent in Canada. Conditions at "PMU" farms vary, and some farms work very diligently to place their unwanted foals. Many others are not as responsible.
Many "PMU" babies are well bred, and some are even registered purebreds. "PMU" foals can be adopted online through rescue groups, but most of the foals bred in Canada are sold directly to meat processing plants. In Canada, a "PMU" filly has a less than one in ten chance of escaping slaughter. A colt is almost certainly doomed, with a less than one in fifty chance at life. The mares suffer a much more grim outlook, as they are not sold until they are no longer able to become pregnant, and at that point many are too foul tempered to be desirable. "PMU" foals can be very rewarding to work with, as they frequently have not been handled before rescue, and for all intents and purposes should be considered wild.
For more detailed information about Premarin, please visit www.premarin.org. Not only are they a well researched source of information, but they also provide a link to an online petition to stop the production of Premarin.