While the adoption of genomic evaluations in livestock has increased genetic gain rates, its effects on genetic diversity and accumulation of inbreeding have raised concerns in cattle populations. Increased inbreeding may affect fitness and decrease the mean performance for economically important traits, such as fertility and growth in beef cattle, with the age of inbreeding having a possible effect on the magnitude of inbreeding depression. The purpose of this study was to determine changes in genetic diversity as a result of the implementation of genomic selection in Angus cattle and quantify potential inbreeding depression effects of total pedigree and genomic inbreeding, and also to investigate the impact of recent and ancient inbreeding. We found that the yearly rate of inbreeding accumulation remained similar in sires and decreased significantly in dams since the implementation of genomic selection. Other measures such as effective population size and the effective number of chromosome segments show little evidence of a detrimental effect of using genomic selection strategies on the genetic diversity of beef cattle. We also quantified pedigree and genomic inbreeding depression for fertility and growth. While inbreeding did not affect fertility, an increase in pedigree or genomic inbreeding was associated with decreased birth weight, weaning weight, and post-weaning gain in both sexes. We also measured the impact of the age of inbreeding and found that recent inbreeding had a larger depressive effect on growth than ancient inbreeding. In this study, we sought to quantify and understand the possible consequences of genomic selection on the genetic diversity of American Angus cattle. In both sires and dams, we found that, generally, genomic selection resulted in decreased rates of pedigree and genomic inbreeding accumulation and increased or sustained effective population sizes and number of independently segregating chromosome segments. We also found significant depressive effects of inbreeding accumulation on economically important growth traits, particularly with genomic and recent inbreeding.

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基因组选择下美国安格斯牛的遗传多样性趋势和近亲繁殖的影响

虽然在牲畜中采用基因组评估提高了遗传增益率，但其对遗传多样性和近亲繁殖积累的影响引起了牛群的关注。近亲繁殖的增加可能会影响健康并降低经济重要性状的平均性能，例如肉牛的生育力和生长，近亲繁殖的年龄可能对近亲繁殖抑制的程度产生影响。本研究的目的是确定安格斯牛实施基因组选择后遗传多样性的变化，量化总谱系和基因组近交的潜在近交抑制效应，并调查近代和古代近交的影响。我们发现，自实施基因组选择以来，公牛的近交积累年率保持相似，而在水坝中则显着下降。其他措施，如有效种群规模和染色体片段的有效数量，几乎没有证据表明使用基因组选择策略对肉牛的遗传多样性有不利影响。我们还量化了生育和生长的谱系和基因组近亲繁殖抑制。虽然近亲繁殖不影响生育能力，但血统或基因组近亲繁殖的增加与两性的出生体重、断奶体重和断奶后体重下降有关。我们还测量了近亲繁殖年龄的影响，发现近期近亲繁殖对生长的抑制作用比古代近亲繁殖更大。在这项研究中，我们试图量化和了解基因组选择对美国安格斯牛遗传多样性的可能影响。在公牛和母猪中，我们发现，一般来说，基因组选择导致谱系和基因组近亲繁殖率降低，并增加或维持有效种群大小和独立分离染色体片段的数量。我们还发现近亲繁殖积累对经济上重要的生长性状有显着的抑制作用，尤其是基因组和最近的近亲繁殖。基因组选择导致谱系和基因组近交积累率降低，并增加或维持有效种群大小和独立分离染色体片段的数量。我们还发现近亲繁殖积累对经济上重要的生长性状有显着的抑制作用，尤其是基因组和最近的近亲繁殖。基因组选择导致谱系和基因组近交积累率降低，并增加或维持有效种群大小和独立分离染色体片段的数量。我们还发现近亲繁殖积累对经济上重要的生长性状有显着的抑制作用，尤其是基因组和最近的近亲繁殖。