PDF(Pubmed)
Abstract：
BACKGROUND: Genetic diversity is a necessary condition for populations to evolve under natural adaptation, artificial selection, or both. However, genetic diversity is often threatened, in particular in domestic animal populations where artificial selection, genetic drift and inbreeding are strong. In this context, cryopreserved genetic resources are a promising option to reintroduce lost variants and to limit inbreeding. However, while the use of ancient genetic resources is more common in plant breeding, it is less documented in animals due to a longer generation interval, making it difficult to fill the gap in performance due to continuous selection. This study investigates one of the only concrete cases available in animals, for which cryopreserved semen from a bull born in 1977 in a lost lineage was introduced into the breeding scheme of a French local dairy cattle breed, the Abondance breed, more than 20 years later.
RESULTS: We found that this re-introduced bull was genetically distinct with respect to the current population and thus allowed part of the genetic diversity lost over time to be restored. The expected negative gap in milk production due to continuous selection was absorbed in a few years by preferential mating with elite cows. Moreover, the re-use of this bull more than two decades later did not increase the level of inbreeding, and even tended to reduce it by avoiding mating with relatives. Finally, the reintroduction of a bull from a lost lineage in the breeding scheme allowed for improved performance for reproductive abilities, a trait that was less subject to selection in the past.
CONCLUSIONS: The use of cryopreserved material is an efficient way to manage the genetic diversity of an animal population, by mitigating the effects of both inbreeding and strong selection. However, attention should be paid to mating of animals to limit the disadvantages associated with incorporating original genetic material, notably a discrepancy in the breeding values for selected traits or an increase in inbreeding. Therefore, careful characterization of the genetic resources available in cryobanks could help to ensure the sustainable management of populations, in particular local or small populations. These results could also be transferred to the conservation of wild threatened populations.
RESULTS: We found that this re-introduced bull was genetically distinct with respect to the current population and thus allowed part of the genetic diversity lost over time to be restored. The expected negative gap in milk production due to continuous selection was absorbed in a few years by preferential mating with elite cows. Moreover, the re-use of this bull more than two decades later did not increase the level of inbreeding, and even tended to reduce it by avoiding mating with relatives. Finally, the reintroduction of a bull from a lost lineage in the breeding scheme allowed for improved performance for reproductive abilities, a trait that was less subject to selection in the past.
CONCLUSIONS: The use of cryopreserved material is an efficient way to manage the genetic diversity of an animal population, by mitigating the effects of both inbreeding and strong selection. However, attention should be paid to mating of animals to limit the disadvantages associated with incorporating original genetic material, notably a discrepancy in the breeding values for selected traits or an increase in inbreeding. Therefore, careful characterization of the genetic resources available in cryobanks could help to ensure the sustainable management of populations, in particular local or small populations. These results could also be transferred to the conservation of wild threatened populations.
摘要：
背景：遗传多样性是种群在自然适应下进化的必要条件，人工选择，或者两者兼而有之。然而,遗传多样性经常受到威胁，特别是在人工选择的家畜种群中，遗传漂变和近亲繁殖很强烈。在这种情况下，冷冻保存的遗传资源是重新引入丢失的变异和限制近亲繁殖的有希望的选择。然而,虽然古代遗传资源的使用在植物育种中更为普遍，由于更长的世代间隔，它在动物中的记载较少，由于连续选择，很难填补性能空白。这项研究调查了动物中唯一可用的具体案例之一，为此，将1977年出生的公牛的冷冻保存的精液引入了法国当地奶牛品种的育种计划，Abondance品种,20多年后。
结果：我们发现这种重新引入的公牛相对于当前种群在遗传上是不同的，因此可以恢复随时间损失的部分遗传多样性。由于连续选择而导致的预期牛奶产量的负差距在几年内通过与优秀奶牛的优先交配而被吸收。此外，二十多年后重新使用这头公牛并没有提高近亲繁殖的水平，甚至倾向于通过避免与亲戚交配来减少它。最后,在育种计划中从失去的血统中重新引入公牛可以提高繁殖能力的性能，一种过去不太容易被选择的特征。
结论：使用冷冻保存的材料是管理动物种群遗传多样性的有效方法，通过减轻近亲繁殖和强选择的影响。然而,应注意动物的交配，以限制与纳入原始遗传物质相关的缺点，特别是选定性状的育种值差异或近交增加。因此,对冷冻库中可用的遗传资源进行仔细表征有助于确保种群的可持续管理，特别是当地或小人口。这些结果也可以转移到野生受威胁种群的保护中。
结果：我们发现这种重新引入的公牛相对于当前种群在遗传上是不同的，因此可以恢复随时间损失的部分遗传多样性。由于连续选择而导致的预期牛奶产量的负差距在几年内通过与优秀奶牛的优先交配而被吸收。此外，二十多年后重新使用这头公牛并没有提高近亲繁殖的水平，甚至倾向于通过避免与亲戚交配来减少它。最后,在育种计划中从失去的血统中重新引入公牛可以提高繁殖能力的性能，一种过去不太容易被选择的特征。
结论：使用冷冻保存的材料是管理动物种群遗传多样性的有效方法，通过减轻近亲繁殖和强选择的影响。然而,应注意动物的交配，以限制与纳入原始遗传物质相关的缺点，特别是选定性状的育种值差异或近交增加。因此,对冷冻库中可用的遗传资源进行仔细表征有助于确保种群的可持续管理，特别是当地或小人口。这些结果也可以转移到野生受威胁种群的保护中。
