基因组选择对法国三个奶牛品种遗传多样性和遗传增益的影响。
The impact of genomic selection on genetic diversity and genetic gain in three French dairy cattle breeds.
机构信息
GABI, INRA, AgroParisTech, Université Paris-Saclay, 78350, Jouy-en-Josas, France.
ALLICE, Paris, France.
出版信息
Genet Sel Evol. 2019 Sep 23;51(1):52. doi: 10.1186/s12711-019-0495-1.
BACKGROUND
In France, implementation of genomic evaluations in dairy cattle breeds started in 2009 and this has modified the breeding schemes drastically. In this context, the goal of our study was to understand the impact of genomic selection on the genetic diversity of bulls from three French dairy cattle breeds born between 2005 and 2015 (Montbéliarde, Normande and Holstein) and the factors that are involved.
METHODS
We compared annual genetic gains, inbreeding rates based on runs of homozygosity (ROH) and pedigree data, and mean ROH length within breeds, before and after the implementation of genomic selection.
RESULTS
Genomic selection induced an increase in mean annual genetic gains of 50, 71 and 33% for Montbéliarde, Normande and Holstein bulls, respectively, and in parallel, the generation intervals were reduced by a factor of 1.7, 1.9 and 2, respectively. We found no significant change in inbreeding rate for the two national breeds, Montbéliarde and Normande, and a significant increase in inbreeding rate for the Holstein international breed, which is now as high as 0.55% per year based on ROH and 0.49% per year based on pedigree data (equivalent to a rate of 1.36 and 1.39% per generation, respectively). The mean ROH length was longer for bulls from the Holstein breed than for those from the other two breeds.
CONCLUSIONS
With the implementation of genomic selection, the annual genetic gain increased for bulls from the three major French dairy cattle breeds. At the same time, the annual loss of genetic diversity increased for Holstein bulls, possibly because of the massive use of a few elite bulls in this breed, but not for Montbéliarde and Normande bulls. The increase in mean ROH length in Holstein may reflect the occurrence of recent inbreeding. New strategies in breeding schemes, such as female donor stations and embryo transfer, and recent implementation of genomic evaluations in small regional breeds should be studied carefully in order to ensure the sustainability of breeding schemes in the future.
背景
法国于 2009 年开始在奶牛品种中实施基因组评估，这极大地改变了育种计划。在这种情况下，我们研究的目的是了解基因组选择对 2005 年至 2015 年间出生的三种法国奶牛品种（蒙贝利亚、诺曼底和荷斯坦）公牛遗传多样性的影响及其涉及的因素。
方法
我们比较了实施基因组选择前后各品种的年度遗传增益、基于同源单体型（ROH）和系谱数据的近交率以及平均 ROH 长度。
结果
基因组选择使蒙贝利亚、诺曼底和荷斯坦公牛的平均年度遗传增益分别增加了 50%、71%和 33%，同时，世代间隔分别缩短了 1.7 倍、1.9 倍和 2 倍。我们发现，两个国家品种（蒙贝利亚和诺曼底）的近交率没有显著变化，而国际品种（荷斯坦）的近交率显著增加，现在基于 ROH 的近交率为 0.55%/年，基于系谱数据的近交率为 0.49%/年（相当于每代 1.36%和 1.39%）。荷斯坦公牛的平均 ROH 长度比其他两个品种的公牛长。
结论
随着基因组选择的实施，三个主要的法国奶牛品种公牛的年度遗传增益增加。与此同时，荷斯坦公牛的遗传多样性每年损失增加，这可能是由于该品种大量使用少数精英公牛造成的，但蒙贝利亚和诺曼底公牛的遗传多样性没有损失。荷斯坦牛平均 ROH 长度的增加可能反映了近期近交的发生。未来应仔细研究育种计划中的新策略，如雌性供体站和胚胎移植，以及小型地区品种最近实施的基因组评估，以确保未来育种计划的可持续性。
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