Breeding healthy, sound dogs that are good examples of their breed requires having a plan. Most breeders can tell you today which dogs they plan to breed together to produce their next two to three litters.
“Breeding requires having a vision,” says Anita Oberbauer, PhD, professor of animal science and associate dean in the College of Agricultural and Environmental Sciences at the University of CaliforniaDavis. “You must define your objectives and goals. The hallmark of a good breeder is making progress toward the overall objectives.”
It is estimated that between 1 and 5 percent of a breed produces the next generation. Selection for quality and maintaining different bloodlines are important to preserve breed health and genetic diversity. The ability to balance positive traits and deleterious mutated genes is fundamental to breeding.
Dog breeds were produced by linebreeding on a small group of founding canine ancestors. Breeders selected for purposefully bred litters based on phenotype, form and function. In some breeds, deleterious mutated genes, primarily recessive genes, accumulated in the background of their gene pool.
“The most common genetic diseases seen by veterinarians every day in their practices are due to ancient liability genes that originated in ancestors that preceded the separation of breeds,” explains Jerold Bell, DVM, adjunct professor of genetics at the Cummings School of Veterinary Medicine at Tufts University. “These include allergies, hip dysplasia, heart diseases, cataracts, cruciate ligament disease, hereditary cancers, and others. They occur in purebred and mixed-breed dogs.”
Although many rare identified mutations are autosomal recessive, the majority of heritable diseases are polygenic or complex, says Leigh Anne Clark PhD, associate professor of genetics at Clemson University. “To help maintain genetic diversity, breeders should consider reducing the number of times a sire or dam is bred,” she says. “You also have to look at the impact of environmental factors, such as stress, toxins, hormones, activity level, diet, and even ultraviolet exposure, on disease conditions.”
Genetic experts advise dog breeders to always strive to produce quality, healthy dogs. Using different types of mating tools will help mix breeding lines and maintain genetic diversity. Here are types of matings used in dog breeding:
- Linebreeding is a mating between dogs more closely related than the average for the breed. It should be used to solidify traits in your bloodline.
- Outbreeding is a mating between dogs less related than the average for the breed. It should be used to bring in traits that a particular dog does not have. If you consistently outbreed, it removes the differences between dogs and thus reduces the ability to select for individual traits.
It is important to keep in mind the value of having strong brood bitches in dog breeding programs. Females have two X chromosomes, whereas males have one X chromosome and one Y chromosome. The Y chromosome determines the sex of the offspring and codes for “male” traits, but the X chromosome contains a full contingency of genetic information. Keep in mind, too, it is possible that dogs from far back in a pedigree may have as strong an influence genetically than the parents or grandparents.
Great dog breeders never compromise on the absolutes of their breed standard and what defines breed type, yet they are able to influence subtle points to produce outstanding dogs. Healthy bloodlines and healthy breeds start with a vision and then working to accomplish these goals.