Although female dogs start going into heat at the age of 6 months, they should not be bred until their second season, which is usually six months later. Males reach sexual maturity sometime between the ages of 12 to 15 m... More »

The greyhound is the fastest dog breed and, perhaps, the second fastest land animal behind the cheetah. Greyhounds reach speeds as high as 45 miles per hour in an open run and achieve maximum velocity in six strides over... More »

www.reference.com Pets & Animals Pets Dogs

On average, dogs run about 19 miles per hour. Although breeds vary tremendously, many types of dogs run much faster. Greyhounds run 45 miles per hour, and the Saluki runs even faster in short, 1/2 mile distances. For sho... More »

Canines typically menstruate twice each year, with most coming into heat every 6 months, although menstrual rates vary among breeds. Small dogs typically begin menstruating at earlier ages than female canines of larger b... More »

The fertility of male dogs varies depending on breed and size, but most male dogs begin to reach sexual maturity at six months of age. It often takes a few extra months for larger dogs to become fertile. More »

www.reference.com Pets & Animals Pets Dogs

Female Labrador Retrievers go into their first heat between 6 and 24 months of age, which is the same age range that all dogs are given. The Labrador Retriever breed tends to be toward the latter end of this age range du... More »

Although a female Shih Tzu has her first heat at 6 months, AllShihTzu.com states that it is not safe to breed her until her second heat at least. She should only have three litters total and stop breeding once she turns ... More »