History of PMU in Horses

PMU, which stands for pregnant mare urine, is sold in the form of the drug Premarin and was the first menopausal treatment and estrogen replacement. Women throughout North America were grateful for Premarin, but PMU farms and treatment of the horses have been scrutinized for years. A battle continues between the pharmaceutical companies, the ranchers they employ and animal rights activists.

  1. Discovery

    • In 1930, the Canadian pharmaceutical company Ayerst, McKenna, &Harrison Ltd. discovered water-soluble estrogen. The hormone was extracted from women late in their pregnancies and taken orally by menopausal and postmenopausal women. It treated symptoms such as hot flashes, prevented osteoporosis and functioned as an estrogen replacement. Researchers soon found that the urine of pregnant horses contained water-soluble, conjugated estrogen necessary for menopausal and postmenopausal relief in a more potent and attainable form.

    Beginning of PMU Farming

    • PMU farms were started in Quebec, Canada. Mares were kept in pastures with stallions to breed. Once the mares were in the third or fourth month of pregnancy, with estrogen levels at their peak, they were brought inside and kept in small tie stalls. The mares were fitted with urine collection devices (UCDs) and remained in their stalls for the last six months of their pregnancies.

    Introduction and Early Success of Premarin

    • Premarin was introduced in Canada in 1941 and in the U.S. in 1942. It was the first hormone replacement therapy (HRT) available to menopausal and postmenopausal women and became widely used by this group.

    PMU Farm Expansion

    • With the success of Premarin, the pharmaceutical company decided to establish PMU farms in Ontario, upstate New York and Vermont. In the 1960s and '70s, PMU farms moved beyond the East Coast, and many thrived in the Midwest regions of Canada and the United States.

    Equine Welfare Controversy

    • Many foals, byproducts of the PMU industry, were sent to slaughter

      While women benefited from PMU farms, the horses suffered. Laws passed in the 1960s attempted to improve equine conditions. Concerns included lack of exercise, subpar nutrition, ill-fitting UCDs and inhumane living conditions for the six months they were kept in standing in tie stalls. The foals were usually sent to slaughter.

    Public Awareness and Foundation of the NAERIC

    • In 1986, HorseAid was the first animal rights group to investigate PMU farms. HorseAid published its findings in print and on the Internet, including horrific details and pictures about conditions of the mares and treatment of their foals. In 1995, the North American Equine Ranching Information Council (NAERIC) formed to advocate for the humane management of pregnant mares. The council breeds registered horses and sells their foals mainly to families and show barns.

    Estrogen Alternatives and the Decline of the PMU Industry

    • Public unease about PMU farms caused a demand for alternative treatment. Many synthetic and non-PMU treatments are available today, including Estraderm and Fosomax. While many women still use Premarin, overall sales have decreased dramatically since the 1990s. Consequently, many PMU farms have closed. Equine welfare organizations throughout North America are working to place former PMU mares and their foals with families.