Did you know you can eliminate Chestnut's chances of ever getting mammary cancer if you spay her before her first heat?
In dogs, a female spayed before her first heat will have a near-zero chance of developing mammary cancer. After the first heat, this incidence climbs to 7 percent, and after the second heat, the risk is 25 percent. If your pet has already gone through one or more heats, we still recommend spaying. Spaying can help shrink mammary cysts and prevents pyometra. http://www.cvm.umn.edu/vmc/forclient...rbenefits.html
Please do not breed her. You don't have the time or the right reasons for doing so. Breeding should be left to the experts.