The phrase "accidental breeding" refers to the unplanned or unintentional mating between animals, resulting in offspring being born unexpectedly. Full definition
Ideally, the main goal of neutering is to prevent accidental breeding or increasing the breed's population but some do this to create an effect on a dog's growth rate. (thebarkbuzz.com)
We were inundated with puppies and kittens, many of which were the result of accidental breeding of young adult animals on their first heat cycle. (2ndchance.info)
Euthanasia is the fate of about two million dogs each year, many from accidental breedings by the neighbor's loose dog. (canismajor.com)