2019 Breed Report Executive Summary
“What is needed is for breeders to think in population terms… to look at each breed genetically as a population and each breeder involved with that particular population as a conservator of that breed in partnership with others.” ~ J. Bragg
Our goal is to help English Shepherd breeders produce healthy dogs today and in the future. In this first report we examine breed health and compare current breeding practices to recommended conservation principles. Our goal is to assist breeders as they consider their breeding priorities and the needs of the breed. Below is a summary of key findings; you can view the full report online here at 2019 Breed Report
English Shepherd Population: Brief History
The English Shepherd (ES) breed was developed in the early 20th century from a large, diverse, group of founders. The generous population size that characterized ES in the early to mid-1900s was followed by a general decline in the latter part of the century. The population began rebounding again in the late 1990s. Growth in numbers is necessary to maintain a viable breed but population growth must be supported by healthy breeding practices in order to maintain genetic diversity and founder lines.
Key Findings OF the report, Including Breed Fitness indicators
Population Growth. Population growth has been steady over the past 12 years. Effective population size (breeding population) has more than doubled. The ratio of sires to dams has remained relatively constant at 3:4.
Reproductive Characteristics. Average litter size is 7.5 pups/litter and less than 1% of pups are stillborn. Only 15% of litters include a stillbirth and 94% of pups survive to weaning. Most breeding dogs produce only one or two litters in their lifetime; dogs producing 3 or more litters may have a disproportionately large impact on the next generation.
Founder balance and genetic diversity. Genetic diversity of a breed is determined by the size and diversity of the founding population and the number of descendants representing them. Population declines (genetic bottlenecks), like that experienced by ESs in the 1980s, may increase inbreeding and reduce genetic diversity through loss of founding lines.
Some sire and dam lines are hanging on by a thread. Data on sires, dams, and registered litters in the ESCR between 2013 and 2018 suggests that certain founders are in danger of disappearing from the gene pool:
- For sire lines, the five most common founders are represented in 55% of the litters (399 litters) while the five least common are found in only 2.4% of the litters (17 litters).
- For dam lines, the five most common founders are represented in 56% of the litters (403 litters) while the five least common are found in less than 1% of the litters (5 litters).
Increase in inbreeding. Pedigree-based coefficients of inbreeding (COI) have increased significantly in the last 10 years. Genetic COI, measured by DNA analysis, appear to be substantially higher than pedigree-based COI. The average level of inbreeding is increasing by either measure and the average COI currently exceeds recommended thresholds.
Generation time. Generation time is the interval between one generation and the next. Genetic loss occurs with every generation in purebred dogs. Genetic experts suggest that to retain genetic diversity, breeds should have an average generation time of 5+ years. Average generation time can be increased by breeding older (4–6 year old) pairs of dogs or by breeding younger dogs to older mates. In addition to preserving genetic diversity, longer generation times also improve selection for health and vitality.
- Short generation time is currently reducing genetic diversity in ES.
- Review of a random sample of 100 litters born between 2007 and 2017 showed 69% of ES litters have a generation time of less than 4 years.
Sibling contribution. The number of puppies from each litter (i.e., unique breeding cross) that go on to become breeding stock for the next generation influences genetic diversity. Lack of sibling contribution (few or no puppies per litter going on to be bred) appears to be an important factor in the reduction of genetic diversity in ESs. As of the end of 2018:
- 43% of the 2010-11 litters had NO puppies reproduce (0% of the next generation)
- 36% of the 2010-11 litters had ONE puppy that reproduced (36% of the next generation)
- 21% of the 2010-11 litters had TWO OR MORE puppies that reproduced (64% of the next generation)
- Fewer males than females reproduced, reducing effective breeding population size.
In order to retain genetic diversity from one generation to the next, breeders should avoid repeat breedings and strive to ensure that at least two pups from every litter (barring obvious defects) contribute to the next generation.
Genetic Load. The “genetic load” of a breed consists of the genes within the population that can damage fitness of individual dogs. Genetic load cannot be eliminated, but breeders can monitor genetic defects, and avoid breeding combinations that decrease the likelihood that genetic disorders are expressed. Screening your breeding stock is recommended if you do not know the genotype of your dogs’ parents. The following mutations are known to occur in ESs:
- MDR-1 – results in sensitivity to certain medications
- Collie Eye Anomaly – may result in thinning of the retina and vision problems
- Progressive Retinal Atrophy-prcd – causes deterioration in the retina with age
- Degenerative Myelopathy – associated with risk for neuromuscular disease
- Dilated Cardiomyopathy – associated with risk for heart disease in some breeds
- Hyperuricosemia – increases risk of developing urinary stones
In the past, ES breeders have had to make decisions without benefit of information on the population as a whole. The breed’s unique history has resulted in a population that appears to experience relatively few genetic disorders. The diversity and vitality that has characterized the breed may be in danger, however, due to increased levels of inbreeding, dwindling numbers of founder lines, and failure to cultivate diversity in breeding stock. Fortunately, each of these problems has a solution and breeders can reverse the trends that threaten breed health.
Recommended Breeding Practices
The following list is excerpted from Jeff Bragg’s article, “Population Genetics in Practice.” You can (and should!) read the whole article online: https://www.seppalakennels.com/articles/population-genetics-in-practice.htm
- Maintain balance of sires and dams
- Avoid incestuous matings (e.g., closer than first cousins)
- Understand and monitor coefficient of inbreeding (COI)
- Pay attention to the trend in COI
- Know the genetic load but don’t obsess over it
- Conserve sire and dam-line diversity
- Maintain high generation time
- Avoid repeat breedings
- Ensure sibling contribution
- Monitor fitness indicators (e.g., fertility and litter size)
- Avoid unfit breeding stock
- Monitor population growth
- Attempt founder balancing (in coordination with other breeders)
The next steps in our research will involve studying the genetic relationship between dogs in the breed. Pedigree is a useful guide but genetic testing of a representative sample of the breed will give us more information. We need your help in order for this to be a success!
If you can help or would like to participate in the English Shepherd Genetic Diversity Study, please contact the English Shepherd Breed Conservancy at email@example.com.
Published by English Shepherd Breed Conservancy