Reconstitution and modernization of lost Holstein male lineages using samples from a gene bank

摘要

More than 99% of all known Holstein artificial insemination(AI) bulls in the United States can be tracedthrough their male lineage to just 2 bulls born in the1950s, and all Holstein bulls can be traced back to 2bulls born in the late 1800s. As the Y chromosome ispassed exclusively from sire to son, this suggests thatvariation is limited for much of the Y chromosome.Two additional male lineages that are separate frommodern lineages before 1890 were present at the startof the AI era and had semen available from the USDANational Animal Germplasm Program (Fort Collins,CO). Semen from representatives of those lineages wereused for in vitro embryo production by mating to elitemodern genetic females, resulting in the birth of 7 bullsand 8 heifers. Genomic evaluation of the bulls suggestedthat lineages from the beginning of the AI era couldbe reconstituted to breed average for total economicmerit in 1 generation when mated to elite females dueto high genetic merit for fertility, near-average geneticmerit for fat and protein yield, and below-average geneticmerit for udder and physical conformation. Semenfrom the bulls is commercially available to facilitate Ychromosome research and efforts to restore lost geneticdiversity.