More than 99% of all known Holstein artificial insemination (AI) bulls in the United States can be traced through their male lineage to just 2 bulls born in the 1950s, and all Holstein bulls can be traced back to 2 bulls born in the late 1800s. As the Y chromosome is passed exclusively from sire to son, this suggests that variation is limited for much of the Y chromosome. Two additional male lineages that are separate from modern lineages before 1890 were present at the start of the AI era and had semen available from the USDA National Animal Germplasm Program (Fort Collins, CO). Semen from representatives of those lineages were used for in vitro embryo production by mating to elite modern genetic females, resulting in the birth of 7 bulls and 8 heifers. Genomic evaluation of the bulls suggested that lineages from the beginning of the AI era could be reconstituted to breed average for total economic merit in 1 generation when mated to elite females due to high genetic merit for fertility, near-average genetic merit for fat and protein yield, and below-average genetic merit for udder and physical conformation. Semen from the bulls is commercially available to facilitate Y chromosome research and efforts to restore lost genetic diversity.

中文翻译：

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使用基因库中的样本重建失落的荷斯坦男性世系并进行现代化改造。

在美国，超过99％的已知霍尔斯坦人工授精（AI）公牛都可以通过其公系追溯到1950年代出生的2头公牛，所有霍尔斯坦公牛都可以追溯到1800年代末出生的2头公牛。 。由于Y染色体仅从父系传给儿子，这表明大多数Y染色体的变异受到限制。在AI时代开始之初，又出现了另外两个与1890年前的现代血统不同的雄性血统，它们的精液可从美国农业部国家动物种质计划（美国科林斯堡）获得。这些血统代表的精液通过与现代现代遗传雌性交配而用于体外胚胎生产，从而产生了7头公牛和8头小母牛。对公牛的基因组评估表明，由于具有高生育力的遗传优势，对于脂肪和蛋白质的近乎平均的遗传优势，当与精英雌性交配时，可以重新构建AI时代开始以来的血统，以获得1代总经济优势的平均值。丰产，乳房和身体构象的遗传价值低于平均水平。公牛的精液可商购，以促进Y染色体研究和恢复丢失的遗传多样性的努力。