|DECHOW, CHAD - PENNSYLVANIA STATE UNIVERSITY|
|LIU, W - PENNSYLVANIA STATE UNIVERSITY|
|SPECHT, L - PENNSYLVANIA STATE UNIVERSITY|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2020
Publication Date: 3/12/2020
Citation: Dechow, C.D., Liu, W.S., Specht, L.W., Blackburn, H.D. 2020. Reconstitution and modernization of lost Holstein male linages using samples from a gene bank. Journal of Dairy Science. https://doi.org/10.3168/jds.2019-17753.
Interpretive Summary: With the adoption of artificial insemination in the 1950s, Holstein male lineages rapidly contracted in purebred dairy cattle populations; all Holstein bulls today can be traced to one of two male lineages. To broaden the genetic base, two bulls with semen from the National Animal Germplasm Program repository were mated to elite modern genetic females to reconstitute two male lineages no longer present in the live Holstein population. Semen is now available from the lost lineages and the bulls are near breed average for milk production, superior for fertility, and below breed average for type conformation.
Technical Abstract: More than 99 percent of all known Holstein artificial insemination bulls in the United States can be traced through their male lineage to just two bulls born in the 1950s and all Holstein bulls can be traced back to two bulls born in the late 1800s. As the Y-chromosome is passed exclusively from sire to son, this suggests there is limited variation for much of the Y-chromosome and that there has been significant loss of genetic diversity in the artificial insemination era. Two additional male lineages that are separate from modern lineages prior to 1890 were present at the start of the artificial insemination era and had semen available from the USDA – National Animal Germplasm Program; 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 seven bulls and eight heifers. Genomic evaluation of the bulls suggested that lineages from the beginning of the artificial insemination era could be reconstituted to breed average for total economic merit in one 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.