Genetic structure and diversity among sheep breeds in the United States: Identification of the major gene pools1,2

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 666 animals from 222 producers located in 38 states. The level of within-breed genetic diversity was variable and not dependent upon status of a breed as a major or minor breed. Bayesian cluster analysis indicated the breeds were grouped more by physiological differences (meat vs. wool production) rather than geographic origin. Results suggest several 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 on collecting germplasm samples for the gene bank. 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.

Genetic diversity of locally adapted sheep from Pantanal region of Mato Grosso do Sul

“…This can be explained by the formation process of the populations, determined by common ancestry, due to their similar function in the sheep industry and supposed racial admixture (Blackburn et al, 2011). In a meta-analysis performed by Paiva et al (2011b), association among these populations was also confirmed, grouping them into the same cluster.…”

Assessment of genetic relationship between six populations of Welsh Mountain sheep using microsatellite markers

“…The level of inbreeding recorded here for the Pedigree WM is an important observation, as Blackburn et al (2011) suggest that breeds with an inbreeding coefficient greater than 0.15 warrant close monitoring. The Nelson WM type, with a coefficient of inbreeding of 0.144, is also close to this value of 0.15, and so may be another population which needs to be carefully monitored.…”

“…Blackburn et al (2011) reported 13% variation among populations and Dixit et al (2011) found 16.5% of variation was due to between breed differences. This difference may be due to the comparatively low number of individual animals involved in the current study, or because this research has largely looked at variation between populations of different phenotypic types within the WM breed rather than difference between breeds per se.…”

“…Examples of investigations including hill breeds, or breeds selected for relatively harsh conditions, from the UK include Lawson- Handley et al (2007) and Bowles et al (2014), with the former including an example of a Welsh breed -the Llanwenog. The only other example of inclusion of a Welsh breed in an investigation was the North American population of Black WM sheep (Blackburn et al 2011), although these sheep may no longer be directly comparable to the population still found in Wales.…”

Effect of Natural Gastrointestinal Parasitic Infection on Carcass Yield and Characteristics of Sudan Desert Sheep

“…Desert sheep comprise about 80% of the slaughtered sheep in Sudan which greatly contributes in supplying both local markets and exportation [1]. Gastrointestinal nematodes represent a major production problem for ruminant which might be due to a combination of several factors such as climate, level of dietary energy, age, and sheep general health [2,3]. Helminthiasis cause loss of production through mortality, weight loss and reduced meat production leading to serious industrial and economic losses [4].…”