Genetic Diversity of US Sheep Breeds

Authors: Blackburn, Harvey; BROWN, M - VIRGINIA STATE UNIV; WILDEUS, S - UNIV OF WYOMING; STOBART, R - AMERICAN LIVESTOCK BREEDS; BIXBY, D - PRAIRIE VIEW A&M; DZAKUMA, J - SUL ROSS UNIV; ERICSSON, S - FORT VALLEY STATE; GETZ, W - UTAH STATE UNIV; COCKETT, N - TUFTS UNIV; MATSAS, D - TEXAS A&M UNIV; Wilson, Carrie - Welsh; Spiller, Scott

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/30/2008
Publication Date: 7/15/2008
Citation: Blackburn, H.D., Brown, M., Wildeus, S., Stobart, R., Bixby, D., Dzakuma, J., Ericsson, S., Getz, W., Cockett, N., Matsas, D., Welsh, C.S., Spiller, S.F. 2008. Genetic Diversity of US Sheep Breeds. Meeting Abstract.

Interpretive Summary: Understanding the genetic relationships between US sheep breeds is useful in developing conservation strategies and actions. A broad sampling of individual sheep from 28 breeds was performed. Breed types included: fine wool, meat types, long wool, hair, prolific, and fat tailed. Blood and semen samples (n=660) were derived from 222 breeders in 38 states. DNA was extracted from the samples and genotyped using the FAO/ISAG panel of 31 microsatellites, however, based on amplification success only 28 markers were used in the analysis. Genotyped data were analyzed using GENALEX, PHYLIP and STRUCTURE. The following breeds were found to have relatively high inbreeding: Columbia (0.60), Gulf Coast Native (0.54), Jacob (0.52), and Targhee (0.62) suggesting genetic diversity is an issue for rare breeds and some commercially popular breeds. The average number of alleles per breed ranged from 3.67 (Black Welsh Mountain) to 7.89 (Rambouillet). Private alleles ranged from one to five and were found in 22 breeds. There were six breeds with no private alleles. Of interest were the high frequencies of three private alleles in the Tunis (0.62 and 0.15) and Warhill (0.30) breeds. Nei’s genetic distances were computed and ranged from 0.08 for Hampshire - Suffolk to 0.80 for the combinations of Blackbelly Barbados – Black Welsh Mountain, and Hog Island – Tunis. Data were clustered using STRUCTURE assuming 28, 20, 19, and 15 clusters; the assignments from these runs suggest the number of clusters for this dataset is 19. Breeds showing a constant grouping with one another included: Rambouillet – Warhill, Hampshire – Suffolk, Barbados Blackbelly – St Croix, Cotswold – Lincoln, and Columbia – Targhee – Dorset – Polypay. These data provide a baseline for determining the degree of genetic similarity/dissimilarity between many US sheep breeds. With this information germplasm collection activities can be refined, thereby ensuring that germplasm collections capture the genetic diversity needed to safely conserve sheep populations.

Technical Abstract: Understanding the genetic relationships between US sheep breeds is useful in developing conservation strategies and actions. A broad sampling of individual sheep from 28 breeds was performed. Breed types included: fine wool, meat types, long wool, hair, prolific, and fat tailed. Blood and semen samples (n=660) were derived from 222 breeders in 38 states. DNA was extracted from the samples and genotyped using the FAO/ISAG panel of 31 microsatellites, however, based on amplification success only 28 markers were used in the analysis. Genotyped data were analyzed using GENALEX, PHYLIP and STRUCTURE. The following breeds were found to have relatively high inbreeding: Columbia (0.60), Gulf Coast Native (0.54), Jacob (0.52), and Targhee (0.62) suggesting genetic diversity is an issue for rare breeds and some commercially popular breeds. The average number of alleles per breed ranged from 3.67 (Black Welsh Mountain) to 7.89 (Rambouillet). Private alleles ranged from one to five and were found in 22 breeds. There were six breeds with no private alleles. Of interest were the high frequencies of three private alleles in the Tunis (0.62 and 0.15) and Warhill (0.30) breeds. Nei’s genetic distances were computed and ranged from 0.08 for Hampshire - Suffolk to 0.80 for the combinations of Blackbelly Barbados – Black Welsh Mountain, and Hog Island – Tunis. Data were clustered using STRUCTURE assuming 28, 20, 19, and 15 clusters; the assignments from these runs suggest the number of clusters for this dataset is 19. Breeds showing a constant grouping with one another included: Rambouillet – Warhill, Hampshire – Suffolk, Barbados Blackbelly – St Croix, Cotswold – Lincoln, and Columbia – Targhee – Dorset – Polypay. These data provide a baseline for determining the degree of genetic similarity/dissimilarity between many US sheep breeds. With this information germplasm collection activities can be refined, thereby ensuring that germplasm collections capture the genetic diversity needed to safely conserve sheep populations.