Male dogs can breathe a sigh of relief. The days of removing their testicles to stop them breeding or to curb aggressive behaviour may be numbered. A contraceptive implant that halts testosterone and sperm production for months at a time is expected to gain European approval within weeks, while steps are being taken to enable the drug to be sold in the US.

Both egg and sperm production are controlled by the release of sex hormones from the pituitary gland, which is in turn controlled by gonadotrophin releasing hormone (GnRH).

The implant, developed by Peptech in Macquarie Park, Australia, …