The urine of horses, especially from pregnant mares, serves as a specialized and valuable biological resource. This material contains high concentrations of naturally occurring compounds, including steroid hormones that are chemically similar to those produced in the human body. This specific chemical composition drives a structured industry dedicated to harvesting and processing this equine byproduct for widespread commercial purposes.
Creating Hormone Replacement Medications
The primary modern use for horse urine centers on the production of conjugated estrogen medications used in hormone replacement therapy (HRT) for women. This process involves extracting and refining the specific estrogen compounds found in the urine to create a pharmaceutical product. The most widely known drug derived from this source is Premarin, an acronym for “PREgnant MAres’ urINe.”
The urine contains a complex mixture of conjugated equine estrogens (CEEs), with the two most prevalent compounds being estrone sulfate and equilin sulfate. These hormones, particularly equilin, are unique to equids but interact effectively with human hormone receptors. The manufacturing process begins with treating the collected urine with an alkaline solvent, followed by filtration. Specialized resins then adsorb the estrogen compounds, which are later eluted using a solvent to yield a crude extract for further pharmaceutical refinement. This complex extraction allows for the stable and orally active delivery of the hormone mixture.
The Specific Source: Pregnant Mare Urine
The concentration of hormones in a mare’s urine depends on her reproductive status, which is why the source is exclusively from pregnant mares, giving rise to the term Pregnant Mare Urine (PMU). During gestation, the equine fetus and placenta produce large amounts of estrogens that are excreted in the mare’s urine. The period of highest hormone concentration occurs during the middle to late stages of the mare’s approximately 11-month pregnancy, typically between the third and eighth month.
The collection process takes place on specialized PMU farms, often involving the mare being kept in individual tie stalls for the duration of the collection period. These stalls restrict the mare’s movement, preventing her from lying down completely or turning around, ensuring the proper positioning of the collection apparatus. A collection device is fitted to the mare’s perineum to capture all excreted urine. This physical confinement and continuous collection are necessary to harvest the estrogen-rich fluid before the mare is released to deliver her foal.
Historical and Alternative Applications
Before its use in modern pharmaceuticals, horse urine held significance in earlier attempts at hormone isolation and in agricultural practices. Early in the 20th century, researchers first extracted human estrogens from the urine of pregnant women to create one of the first orally active hormone products. However, the high potency and consistent supply found in pregnant mare urine quickly made it the preferred raw material for large-scale production, as it was approximately two and a half times more concentrated than human urine.
In agriculture, horse urine has long been recognized as a source of plant nutrients, particularly nitrogen. The waste product, combined with feces as manure, contains urea, which is rapidly converted into ammonia, a form of nitrogen readily available for plant uptake. Undiluted horse manure, including the urine component, typically possesses a favorable carbon-to-nitrogen ratio of around 20:1, making it an effective soil amendment in traditional fertilization practices.
Ethical Concerns in the Collection Industry
The process of collecting pregnant mare urine is a subject of controversy and raises persistent animal welfare concerns. The mares are kept in restrictive tie stalls for up to six months of their pregnancy, severely limiting their ability to move, exercise, or engage in natural behaviors. This prolonged confinement can lead to physical ailments and psychological stress.
To maximize the concentration of estrogen, the mares’ water intake is sometimes restricted, which can cause chronic thirst and dehydration. A further ethical concern involves the foals that result from the necessary continuous pregnancies. Since the foals are a byproduct of the industry, many male and some female foals are often sold off to the horse meat industry or auction, a fate heavily criticized by animal welfare organizations.