Developing a Healthy Breeding Program
Jerold S. Bell, DVM Tufts UniversitySummary:
The thought that goes into any mating is your breeding program. Some breeding programs develop one litter at a time: "I'll see what happens here, then plan the next mating accordingly." Long range breeding programs may involve step-wise decisions: "I'll try to achieve these goals in this mating, then breed back to solidify those goals next time."
Goals should be written down, and prioritized. These may fall under the categories of health, conformation, performance, and behavior. Goals can involve increasing trainability or performance, losing a detrimental gene, or acquiring a conformational characteristic. You should determine which traits you wish to retain, and which traits you wish to acquire in the offspring. The mode of inheritance of traits will determine how quickly you can achieve a goal. The response to selection can occur more rapidly with single gene traits, or may take a few generations for polygenic traits.
Genetic diseases that cause death, discomfort, or those that are not treatable, should have a high priority in genetic disease control. An early goal is to decrease the incidence of affected dogs being born. Disorders with a late age of onset are more difficult to control, as genetically affected dogs can be bred before becoming clinically affected. A reliable early test for identification of affected dogs and carrier dogs leads to better management of genetic disorders.
Breeders should understand the limitations of genetic tests to evaluate their results. This includes the age when the test can be performed, and the accuracy of the test. Breeders should understand that linkage based tests do not identify the defective gene, but a marker that lies close on the chromosome. If a crossover occurs between the marker and the defective gene during reproduction, false positive and false negative results will occur.
Individual breeders can use genetic tests to identify carriers, work to breed away from the defective gene(s), and ensure that the defective gene(s) is not reintroduced in future matings. Each breeder will have his or her own rate of progress, depending on the frequency of the defective gene(s) in their own breeding dogs, and which desirable dogs are carriers.
With reliable tests for carriers, you can breed quality carrier dogs to normal dogs. Normal testing offspring who display desirable traits should replace carriers for future breeding stock. This may not occur in one generation. As more breeders work away from the defective gene(s), the problem for the breed as a whole diminishes.
A mistake of some breeders is to think that selection against carriers is unnecessary, as long as affected dogs are not produced. You should never select more carrier offspring in the next generation than the average frequency of carriers in the population. By not selecting against carriers in breeding stock, you are selecting for a carrier frequency of 50 percent, much higher than most breed averages. This almost guarantees that half the quality dogs in your next generation will be carriers.
If a quality, normal testing dog has not been produced after a number of matings, a different method can be used. We can look to the common experience when a top performer does not reproduce itself well, but a littermate produces far better than itself. When left without quality, genetically normal breeding stock, breeding to an average, but genetically normal littermate may ultimately provide the desirable offspring you want.
If a direct test of the genotype is available, the results of the proposed mates will be all that is necessary. If a phenotypic test for polygenic disease is available (such as hip radiographs or CERF examinations), then the results of the proposed mates, their full-sibs (littermates or repeat breedings), and the results of the grandparents and their full-sibs are important. With polygenic disease, the breadth of pedigree (full-sibs) is as important, if not more important than depth of pedigree (parents and grandparents) in visualizing the spectrum of genes that can be passed on. Normal breeding dogs from mostly normal litters are the best candidates for breeding.
If there is no test for carriers, relative risk assessment can be used for genetic counseling. This technique is useful in autosomal or x-linked recessive disorders. It is based on pedigree analysis and knowledge of the known affected and carrier individuals in the pedigree. The downside of this technique is that it applies selective pressure against all relatives with involved pedigrees. Therefore, genetically normal individuals will be selected against. This can adversely impact the gene pool with widely dispersed genes, or in small breeding populations.
Without genetic tests, breeders can still reduce the carrier risk in their matings. If a valuable breeding animal is determined to be a carrier, he or she can be retired from breeding and be replaced with a quality offspring. The genes of the retired dog can be preserved through the selected offspring, but the carrier risk can be cut in half. To further limit the spread of the defective gene, the offspring should only be used in a limited number of carefully planned matings, and should also be replaced with one or two representative offspring. In this way, you are maintaining the good genes of the line, reducing the carrier risk with each generation, and replacing, not adding to the overall carrier risk in the breeding population.
If gene tests are not available, the storage of frozen semen is important for quality dogs with high-risk pedigrees. If tests evolve that can differentiate carrier from genetically normal dogs, offspring from frozen semen matings can be reintroduced into the gene pool. Both DNA (from blood or cheek swabs) and semen should be stored to utilize this method.
The proper use of genetic tests is not one that continually multiplies carriers in a breeding program. It should be geared toward producing quality, genetically normal dogs. The total elimination of defective genes will probably be impossible for most breeds. With an established testing program, the breed can monitor the frequency of the defective gene in the breeding population, and work to decrease the percentage of carriers.
Suggestions to Improved Planned Breedings (by Dr. Carmen L. Battaglia)
Check the following when screening study dogs:
1. Frequency of the desired traits occurring among his ancestors (three generation pedigree)
2. Frequency of the desired traits found among his littermates
3. Number of carriers, affected littermates, and ancestors in his three generation pedigree
4. Number of pups produced with desired traitsSteps to eliminate carriers:
1. Not repeat the breeding
2. Not use the sire/dam again
3. Test the offspring and not breed from carriers
4. Exclude littermates of those affected
5. Not breed to close relatives of those affectedCharacteristics of Good Brood Bitches:
1. Whelps naturally without problems
2. Milk supply sufficient to support litter size
3. Encourages puppies to nurse
4. Careful and calm with pups
5. Is attentive with pups
Biographical Profile
Jerold Bell, DVM, is a Clinical Assistant Professor and Director of the Clinical Veterinary Genetics Course for the Tufts University School of Veterinary Medicine. He was trained in genetics and genetic counseling at Michigan State University, and the University of Missouri. His DVM is from Cornell University. Dr. Bell is a lecturer to both all-breed and individual breed dog clubs. He is a project administrator of genetic disease control programs for national Parent Clubs. He performs genetic counseling through Veterinary Genetic Counseling, and practices small animal medicine at Freshwater Veterinary Hospital in Enfield, CT. He and his wife own Gordon Setters.
Dr. Robert V. Hutchison, who earned his DVM from The Ohio State University, is currently a co-director of the Animal Clinic Northview, Inc., an American Animal Hospital Association certified, ten doctor veterinary practice. Recognized internationally for work with canine frozen semen and canine reproduction, Dr. Hutchison produces approximately 150 frozen semen litters yearly.
Dr. Hutchison is the Director of the International Canine Semen Bank of Ohio, and a member of the American Veterinary Medical Association, the American Animal Hospital Association, the Society for Theriogenology and the Ohio Veterinary Medical Association. He has served on the Continuing Education Committee, the Ethics & Grievance Committee, the Program Committee, and the Racing Committee of the OVMA, as well as being a leader of the Lorain County Veterinary Medical Association and the Canine and Feline Fertility and Sterility Group.
He currently serves as on off-quarter advisor for College of Veterinary Medicine students interested in small animal theriogenology from The Ohio State University, Virginia Tech, Purdue University, Tufts University, Michigan State University and Auburn University. In addition, Dr. Hutchison has authored articles on canine reproduction, in various breed journals and magazines, made television appearances and been featured in such publications as Canine Chronicle and AKC Gazette.
An internationally recognized speaker on canine and feline infertility, reproduction, whelping and pediatrics, Dr. Hutchison also finds time to serve on the Board of Directors of the Samoyed Health and Research Foundation, study the fertility proteins in canine semen with a grant from the AKC Endowment Fund and work as a consultant for Veterinary Forum and the Veterinary Information Network.
Dr. Gary Johnson is on the faculty in the Department of Veterinary Pathobiology in the College of Veterinary Medicine at the University of Missouri. He has a Bachelors Degree from Augsburg College, a PhD from Kansas State University and a DVM from the University of Minnesota. He has postdoctoral training from Johns Hopkins University and the New York State Department of Health. His early research was on bleeding diseases of dogs. For the last ten years his research has focused on the use of DNA markers to study inherited diseases and quantitative traits in dogs and cattle. Dr. Johnson is a breeder and exhibitor of Irish Terriers.
Dr Malcolm B. Willis was born in 1935, in Yorkshire, England, and was educated at Durham University (BSc: 1956) and Edinburgh University (PhD: 1960). He spent some time as a geneticist for the Milk Marketing Board (1960-65), taught abroad from 1965-72 and is currently a Senior Lecturer in Animal Breeding and Genetics at Newcastle University (1972-date). Dr. Willis is the author of nine books including Genetics of The Dog (1989) The German Shepherd Dog, a Genetic History (1992) and The Bernese Mountain Dog Today (1998). He got his first dog in 1953 (a German Shepherd Dog) and has had one ever since. Dr. Willis first judged in 1959 and, currently gives CCs in German Shepherd Dogs and Bernese Mountain Dogs, having judged in ten countries. Chairman of the German Shepherd Dog Breed Council since it began in 1986, Dr. Willis is also the Chairman German Shepherd Dog League of Great Britain and President of the Northern Bernese Mountain Dog Club. He has been awarded the Gold Medal from the Australian German Shepherd Dog Council in 1988, the Dog Writers of America Award in 1992 (for the German Shepherd Dog book). In his spare time, Dr. Willis advises Police forces and lectures around the world. He lives with his wife Helen, six German Shepherd Dogs, nine Bernese Mountain Dogs, two terriers and 30 British shorthaired cats.
Dr. Carmen Battaglia holds a PhD and Masters degree from Florida State University and is an author, researcher and lecturer. He has worked at Emory University, Florida State University, DeKalb College and the University of Tennessee Space Institute. In 1960 he established the Van Cleve Breeding Program. The intervening years included extensive breeding and research. He has authored many books and articles on education and on animals. His articles have appeared in the AKC Gazette, Dog World, Canadian Shepherd Journal, South AfricanDog Magazine, and dog publications in Australia and Ireland.
In 1986 and 1999 his works about dogs and puppies were selected by the Dog Writers Association of America for recognition. His book entitled Breeding Better Dogs is in its fifth printing and is widely used by breeders to upgrade and improve their breeding programs. His most recent book entitled Caring for the German Shepherd has also been recognized nationally.
In 1987 Dr. Battaglia served as chair for the study group on vicious dog legislation in Georgia. Their reports and recommendations have been used as model legislation for changes in dog ordinance laws in several states. He has been very much involved in many aspects of the dog world chairing several important committees such as the National Genetics Committee for the German Shepherd Dog Club of America, the Health and Education Delegates Committee of the AKC, and the AKC's Committee for the Future and Business and Planning Committee.