National Animal Germplasm Program, National Center for Genetic Resources Preservation, ARS, USDA, Ft. Collins, CO 80525, USA.
J Anim Sci. 2011 Aug;89(8):2336-48. doi: 10.2527/jas.2010-3354. Epub 2011 Mar 7.
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.
了解绵羊品种现有的遗传多样性水平有助于就地和异地保护活动。之前没有对美国绵羊品种进行全面评估；因此，我们评估了 28 个美国绵羊品种之间和内部的遗传多样性。主要和次要品种都包括在分析中，共有来自 38 个州的 222 个生产者的 666 只动物。品种内遗传多样性的水平是可变的，而不取决于品种作为主要或次要品种的地位。贝叶斯聚类分析表明，品种的分组更多地是基于生理差异（肉用与毛用生产），而不是地理起源。研究结果提出了一些可行的措施来改善就地和异地保护。结果清楚地确定了需要增加就地和异地管理的品种（例如，霍格岛和卡拉库尔），并为羊群的就地管理提出了一些建议。相反，有几个品种在遗传上似乎相似，因此在基因库中收集种质样本的工作需要减少。商业上重要的品种（例如，兰布赖特和萨福克）被发现有很大的变异，这应该使饲养者能够不受遗传多样性的困扰，继续进行最大限度地提高利润的选择策略。
