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Title: Genetic Structure and Diversity among U.S. sheep breeds: Identification of the major gene pools.

Author
item Blackburn, Harvey
item PAIVA, SAMUEL - Embrapa Genetic Resources
item WILDEUS, STEPHAN - Virginia State University
item GETZ, WILL - Fort Valley State University
item STOBART, ROBERT - University Of Wyoming
item BIXBY, DON - American Livestock Breeds
item Purdy, Phil
item Wilson, Carrie - Welsh
item Spiller, Scott
item Brown, Michael

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/7/2011
Publication Date: 3/7/2011
Citation: Blackburn, H.D., Paiva, S.R., Wildeus, S., Getz, W., Stobart, R., Bixby, D., Purdy, P.H., Welsh, C.S., Spiller, S.F., Brown, M.A. 2011. Genetic Structure and Diversity among U.S. sheep breeds: Identification of the major gene pools. Journal of Animal Science. 89:2336-2348.

Interpretive Summary: Utilization of molecular DNA markers provides an opportunity to explore genetic diversity within and among livestock populations. Such information serves to clarify how unique breeds may be from one another, as well as, indicating if a breed ranks low in measures of diversity (e.g., number of alleles per loci, or inbreeding levels). In addition, such information can also be used in developing germplasm collections for breeds of interest. This study reports the first comprehensive assessment of genetic diversity measures of 28 sheep breeds found in the US. Both major and minor breeds were included in the analysis and consisted of 660 hd from 222 producers which were located in 38 states. Results suggest a number of actionable items to improve in situ and ex situ conservation. The results clearly identify breeds in need of increased in situ and ex situ management (e.g., Hog Island and Karakul) and allow several suggestions for in situ management of flocks. Conversely, several of the breeds appear genetically similar and therefore require less emphasis in collecting germplasm samples for the gene bank. The commercially important breeds (e.g., Rambouillet and Suffolk) were found to have substantial variation which should enable breeders to proceed, unencumbered by genetic diversity concerns, with selection strategies that maximize profit.

Technical Abstract: Understanding existing levels of genetic diversity of sheep breeds facilitates in situ and ex situ conservation activities. A comprehensive evaluation of US sheep breeds has not been previously performed therefore we evaluated the genetic diversity among and within 28 US sheep breeds. Both major and minor breeds were included in the analysis and consisted of 660 hd from 222 producers which were located in 38 states. The level of within breed genetic diversity was variable and not dependent upon a breed’s status as a major or minor breed. Clustering breeds via STRUCTURE indicated the breeds where grouped more by physiological differences (meat vs wool production) rather than geographic origin. Results suggest a number of actionable items to improve in situ and ex situ conservation. The results clearly identify breeds in need of increased in situ and ex situ management (e.g., Hog Island and Karakul) and allow several suggestions for in situ management of flocks. Conversely, several of the breeds appear genetically similar and therefore require less emphasis in collecting germplasm samples for the gene bank. The commercially important breeds (e.g., Rambouillet and Suffolk) were found to have substantial variation which should enable breeders to proceed, unencumbered by genetic diversity concerns, with selection strategies that maximize profit.