Texas A&M Testing Oral Contraceptives for Animals

Researchers are testing oral contraceptives, used in much the same way as in humans, and the results are promising, says Duane Kraemer, a professor in veterinary physiology and pharmacology and a world leader in embryo transfer who has been involved in cloning four different species in recent years.

Coyote in Texas (Photo courtesy Texas Parks and Wildlife)

"No one method will be useful in all situations," he says.

In Texas, feral hogs have become a severe nuisance to farmers and ranchers, and the state has an estimated three to four million feral hogs, by far the most in the country. Deer also are becoming a problem to more communities each year.

"This approach inhibits maturation of the egg and therefore prevents fertilization," explains Kraemer. "The animals continue to cycle, so it will not yet be ideal for many pet owners. But there is an advantage for use in wild and feral animals."

The technical name for the drug is called a phosphodiesterase 3 inhibitor, and it is one member of a family of drugs being tested as animal contraceptives.

"A spinoff of this contraceptive could probably be used on many different species," Kraemer says. Similar compounds have been tested in laboratories elsewhere in mice and monkeys.

The $90,000 project is being funded by the U.S. Department of Agriculture and private donations.

The pill works by inhibiting the maturation of the egg, not the entire cycle, Kraemer says.

"We are confident we can develop this pill in the not too distant future, but we still have plenty of tests to complete," he says. "It's an exciting and much-needed project, but more funds will be needed, especially since deer and wild pigs are consumed by humans. One of the more interesting challenges will be to develop methods for feeding it to the target animals without affecting other species."

The compound can be mixed with animal feed and must be eaten daily during the critical time. It may also be encapsulated to decrease the frequency it has to be consumed.

"We believe we are the first to test this compound for this specific purpose," Kraemer says. "We're trying new uses for this previously approved compound."

When perfected, the pill could eventually be used as an oral contraceptive for pets, but that application will take some time to develop, Kraemer says. In dogs, for example, the ovulation process is especially complex, but researchers are confident such a birth control pill can one day be successful.

According to the American Humane Society, about seven million dogs and cats are euthanized each year at animal shelters. One female cat can lead to the production of 420,000 offspring in her lifetime.

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