The most commonly known drug containing conjugated equine estrogen,which is derived from pregnant mare’s urine (PMU), is Premarin manufactured by Pfizer Inc.

Premarin is one of the most common prescribe Hormone Replacement Therapy or Menopausal Hormone Therapy drugs to hundreds of thousands of women experiencing menopausal symptoms.

 

Premarin mares are typically Belgian - Quarter Horses crosses.

For their 11-month pregnancies, the mothers are confined to stalls, that are so small that they cannot turn around, lay down or take more than one step in any direction.

 

The mothers must wear rubber urine-collection bags at all times, which causes chafing and lesions, and their drinking water is limited so that their urine will yield more concentrated estrogen.

Once the foals are born, the horses are re-impregnated; this cycle continues for about 12 years.

 

The Foals like Serenity is as heartbreaking as the mothers stories.  Thousands of foals born on PMU farms each year either find themselves as replacements for their exhausted mothers or they along with the 'unusable' mothers are sold to auction and find themselves at slaughterhouses, so these farmers get the last cent out of them as they already didn't make enough money.