Abstract #363

# 363
Genetic update of lost Holstein male lineages.
C. D. Dechow*1, J. Ziegler2, C. G. Sattler2, H. Wei3, H. Blackburn4, 1Pennsylvania State University, University Park, PA, 2Select Sires Inc, Plain City, OH, 3Trans Ova Genetics, Sioux Center, IA, 4National Animal Germplasm Program, Fort Collins, CO.

Only 2 Holstein male lineages remain since the introduction of artificial insemination (AI), suggesting there is limited Y-chromosome variation. Two additional male lines were present at the beginning of the AI era with genetic merit that was comparable to the founders of the current Y-chromosome lineages. The objective of this research was to resurrect and modernize those 2 lost lineages. Semen from ZIMMERMAN ALSTAR PILOT (born in 1954) and a ROSAFE CALIBAN (born in 1953) son from the University of Minnesota control line experiment (CUTHBERT) was available from the National Animal Germplasm Program (NAGP) repository. In vitro produced embryos sired by CUTHBERT were generated at Trans Ova Genetics and implanted as fresh embryos at the Penn State dairy herd (n = 12) with 3 bulls and 3 heifers born in March 2017. PILOT semen had poor motility (3%), but embryos were successfully produced with 15 fresh embryos resulting in 4 Pilot sired bulls and 5 Pilot sired females born in November 2017. Five bulls (2 Caliban sons and 3 Pilot sons) were transferred to Select Sires Inc. for semen collection with Lifetime Net Merit (NM$) values ranging from −$82 (5th percentile) to +$130 (14th percentile) and Lifetime Grazing Merit ranging from −$5 to +$233. All 5 had $NM that exceeded parent average and increased from sire to son 3.4 genetic standard deviations because the bulls were mated to modern elite females and because they have low genomic future inbreeding levels. This research demonstrates that semen stored near the beginning of the AI era is viable and of sufficient quality to facilitate a rapid genetic update of rare or lost lineages. Lower relationship to the commercial population may lead to genetic merit increases that exceed previously published predictions, supporting a broader use of samples maintained in a germplasm repository. Semen from the 5 bulls is commercially available and has been added to the NAGP repository to facilitate research and further efforts to restore lost Y-chromosome lineages. This project will also serve as an evaluation of methods to reintroduce lost genetic diversity during an era of rapid inbreeding.

Key Words: genetic diversity, male lineage, Y chromosome