Dog Male Contraception Instead of Castration

Good times for the male pooches. Their balls will be safe, while they will get friendlier, due to a new contraceptive implant that stops testosterone and sperm production for months. It is expected to obtain European approval within weeks, and it could be also sold in the US.

The production of sex cells (egg and sperm) is controlled by the release of hormones from the pituitary gland, found under the control of gonadotrophin releasing hormone (GnRH).

The implant has been developed by Peptech in Macquarie Park, Australia, and contains a drug called deslorelin (suprelorin), which impairs the GnRH receptors, which won't respond to the GnRH hormone. The drug temporarily stops testosterone production, and besides leaving the dog infertile, low testosterone means a less aggressive behavior. "It's reversible. It gives you the option of breeding later." said Katie Yeates of Peptech.

The six-month implant was launched in Australia in late 2004, and it costs $52-77. Peptech has recently launched a 12-month implant too, and similar implants are being developed for cats and female dogs.

"While oral contraceptives have been used in female cats for years, long-term use may stimulate breast tumors or uterus infections," said David McDowell, veterinary consultant for the UK's Royal Society for the Prevention of Cruelty to Animals.

The new implants act differently, still scientists fear similar side effects might appear, being linked to long-term use in dogs. "Provided owners use them within the manufacturers' guidelines, we would welcome the new drug. However, if dog owners don't want to use their pet for breeding, we believe neutering is the best option."

The European Medicines Agency agreed on the marketing of Suprelorin, which could be found on shelves this month. Last week, a team led by Daniela Braga of the Assisted Fertilization Center in Sao Paolo, Brazil, announced it used the drug as an alternative to surgical sterilization in female cattle to time their pregnancies for the season when pastures are available.