According to a press release from World Horse Welfare, a U.K.-based equine welfare charity, a contraceptive injection will be evaluated in a herd of semiferal ponies residing in Southwest England.

According to the Dartmoor Pony Society, the feral Dartmoor ponies have been living on the moors in Devon since the Middle Ages. As a result of a recent pony population boom, World Horse Welfare, the Dartmoor Hill Pony Association, and Pfizer Animal Health have teamed up to evaluate this possible solution to overbreeding.

In late spring this year, the organization explained, 20 semiferal pony mares will be rounded up, microchipped, marked in a way in which they are identifiable at a distance, and given a contraceptive injection. Veterinarians will administer a second dose four weeks later and evaluate mares after six months to determine if estrous levels have been suppressed. If the test is deemed successful, the test mares will receive a dose to keep them out of estrus until spring 2013.

"We feel that this method of control is advantageous as the mares can come back into foal after the treatment; there is simply a reduction in foal production for the duration of the project," explained Keith C. Meldrum, CB, BVM&S, DVSM, HonFRSH, MRCVS, World Horse Welfare’s veterinary consultant. "We are close to starting the initial injections now that we have the vaccine, provided by Pfizer, in our possession and after the Veterinary Medicines Directorate gave us the go ahead for the vaccine to be imported from Australia into the U.K