Pfizer Canada has announced it will increase the amount of pregnant mare urine (PMU) it collects from its facilities in the Canadian provinces of Manitoba and Saskatchewan in 2016 and 2017.

Pfizer uses PMU to manufacture the hormone replacement therapy drug Premarin, used to treat symptoms of menopause and prevent osteoporosis in post-menopausal women.

According to the Manitoba Co-operator, this is thought to be the first time Pfizer has increased the volume of PMU since it bought the previous Premarin manufacturer, Wyeth Inc., in 2009.

“We can confirm that Pfizer will be increasing our pregnant mare urine (PMU) operations from 2016–2017. It will be a small increase over the current amount that we contract,” wrote Pfizer Canada’s corporate affairs manager Christina Antoniou in an email to Horse Collaborative.

So far, there are no details on how much more urine will be collected, or how many horses will be impacted. According to the North American Equine Ranching Information Council there are currently 19 PMU ranches in Manitoba and Saskatchewan, and 1,300 mares producing urine.

Demand for Premarin declined in recent years following a 2002 Women’s Health Initiative study that found using Prempro (a combination of Premarin and progestin) was linked to an increased risk of breast cancer. (In 2012, the North American Menopause Society released a position statement that continues to support hormone therapy). Animal welfare concerns dealt another blow to the PMU industry as the public learned that as part of the collection protocol mares were confined to stalls for six or more months of the year and continuously impregnated.

“Pfizer has a longstanding commitment to the safety and ethical treatment of horses,” said Antoniou. “We voluntarily adhere to the highest possible standards of humane animal care, standards which meet or exceed relevant local, national, and international regulations for animal care and use.

According to Antoniou, Pfizer is increasing PMU orders after an evaluation of the hormone therapy market and forecasted growth and demand.