Popular sire effect
The popular sire effect (or popular stud/sire syndrome) occurs when an animal with desirable attributes is bred repeatedly. In dog breeding, a male dog that wins respected competitions becomes highly sought after, as breeders believe the sire possesses the genes necessary to produce champions. However, the popular sire effect is not just down to wanting to produce a champion. For example, in Staffordshire Bull Terriers there are several popular sires who are used by breeders to produce specific colours that are not favoured in the show ring. The popular sire is often bred extensively with many females. This can cause undetected, undesirable genetic traits in the stud to spread rapidly within the gene pool. It can also reduce genetic diversity by the exclusion of other males.
While a popular stud can sire a large number of litters, the effect of a popular dam is more limited.[1][2] The constraints of the female reproductive cycle requires dams to have several months in between each litter so, even at capacity, a dam would not be able to parent as many offspring as a sire; furthermore, a dam bred repeatedly may experience a sharp decline in her litter count due to a weaker body caused by too many consecutive pregnancies.[3]
Genetic consequences
Genetic diversity in a population is dependent on the cumulative effects of mutation, natural selection, and population size over many generations.[4] The effective population size (Ne) is the number of individuals in a given population that are able to reproduce and contribute offspring to the next generation. Genetic diversity decays over generations at a rate that is inversely related to the effective population size.[4] In small populations, a major factor that causes a loss of genetic diversity is inbreeding. Intentionally breeding for desirable attributes in a species is known as selective breeding. This process artificially limits the size of the population pool, thereby increasing the rates of inbreeding as well as inbreeding depression, and decreasing a species biological fitness.
Deleterious mutations in
Diseases attributed to the popular sire effect include
In Quarter Horses, hyperkalemic periodic paralysis (HYPP), an autosomal dominant disorder of potassium regulation, can be linked back to a single Quarter Horse sire called Impressive. Also known as Impressive syndrome, HYPP causes heavy muscling in carrier horses, which is a desirable trait in the show ring. However, homozygotes can suffer from severe disease, which manifests as attacks of muscle twitching, weakness, collapse, and death. The disease became widespread when Quarter Horse breeders began selecting for muscling; by 2003, Impressive had over 55,000 descendants. Quarter Horses are now routinely screened for the HYPP gene prior to breeding.
A study of 10 breeds from the UK's
Mitigation methods
The
The
Actions to limit the use of popular sires have been recommended to reduce the loss of genetic diversity in individual breeds.
See also
- Complex vertebral malformation, a widespread lethal genetic disease in Holstein cattle traced back to popular sire Carlin-M Ivanhoe Bell.
- Founder effect
- Population bottleneck
- Artificial selection
References
- ISBN 978-0-8138-0754-6.
- ^ Jerold S Bell (August 2004). "Popular-Sire Syndrome: Keeping watch over health and quality issues in purebreds". AKC Gazette. Retrieved 11 December 2009.
- ^ Breeding Business. The Popular Sire Syndrome in Dog Breeding. Retrieved from breedingbusiness.com/popular-sire-syndrome/. Accessed 2 June 2017.
- ^ a b Frankham, Richard; Ballou, Jonathan; & Briscoe, David. Introduction to Conservation Genetics. Cambridge: Cambridge University Press, 2009. Print.
- ^ Beuchat, Carol. “The Pox of Popular Sires.” The Institute of Canine Biology, http://www.instituteofcaninebiology.org/blog/the-pox-of-popular-sires . Accessed 12 May 2017.
- ^ a b Bell, Jerold S. DVM. “Popular Sire Syndrome and Concerns of Genetic Diversity.” Tufts University Cummings School of Veterinary Medicine. 2003 AKCCHF Health Conference.
- PMID 19531730.
- ^ Sharp, C. A. “The Price of Popularity: Popular Sires and Population Genetics.” The Canine Diversity Project, Vol. IV, No. 3, 1998.
- ^ Haynes, William (1914). "Effect of the popular sire". Journal of Heredity.
- ^ PMID 18493074.
- ^ Association of Zoos & Aquariums. Studbooks. Retrieved from https://www.aza.org/studbooks. Accessed 2 June 2017
- ^ "Doberman Breeders Communicable Diseases". We Love Doodles. 20 June 2022.
- PMID 16420259.
- ^ Indrebo, Astrid (April 2005). "Breeding healthy dogs - a breeders perspective" (PDF). European Journal of Companion Animal Practice. 15 (1). Federation of European Companion Animal Veterinary Associations. Archived from the original (PDF) on 2011-01-05. Retrieved 2010-03-05.
- PMC 4235000.
- ^ "FCI approves breeding strategies 'to enhance genetic health'". Dog World. 4 March 2010. Retrieved 5 March 2010.