Can dogs breed on first heat?

No! No dog should be bred prior to the age of 2 years. Your dog is not mature either mentally or physically. This is pretty basic information about breeding dogs, so ask yourself why you want to breed. If you really think you want to breed your dog,spend the time between now and when she is two years of age learning about dogs and dog breeding. Get knowledgeable before you start bringing more puppies into the world. A good book to start with is Successful Dog Breeding by Walkowicz and Wilcox.