Could Bulls Descending From the 1800s Help Alleviate Inbreeding?
May 14, 2020
There’s no question that inbreeding in Holsteins is increasing—some say to levels approaching alarm.
But help may be on the way—from bulls born in the 19th Century with little or no relationship to 99% of the Holstein population.
A unique breeding project, done in conjunction with Pennsylvania State University, the National Animal Germplasm Program, TransOva Genetics and Select Sires, used semen from bulls from the 1950s that traced their lineage to bulls born in the 1880s. This semen was used to fertilize ova from modern, elite females to create 15 calves. Seven bulls and 8 heifers resulted, and their genomics are now being evaluated.
“Genomic evaluation of the bulls suggest 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 confirmation,” says Chad Dechow, a Penn State geneticist leading the team of researchers on the project.
Bringing this type of genetics back into the Holstein breed is a long-term prospect with no guarantee of success, Dechow says. But the current reclamation project does demonstrate the possibility of using semen from the 1950s to reintroduce lost genetic variation by mating these sires to elite, modern females.
There is no question that inbreeding levels in Holsteins is increasing, reaching an average of 8 percent in 2019. Eight percent is still considered a moderate level, but averages don’t tell the whole story. According to AgSource, which has been collecting and estimating inbreeding since 2011, 76 percent of Holstein cows born in 2011 fell in the low to moderate category of 3.15 to 6.25% inbred. However, Holstein calves born in 2018 now fall in the moderate to high category (82%), which is 6.25 to 12.5%.
The rate of inbreeding has roughly tripled since the introduction of genomics, going from 0.10 percent/year from 2003 to 2008 to 0.31 percent/year from 2013 to 2018. One of the reasons is that generation interval has been cut in half with the use of genomic testing, going from five years to less than three.
The bigger problem is that 99% of Holstein AI sires born in and after 2010 trace to just two bulls: Round Oak Rag Apple Elevation and Pawnee Farm Arlinda Chief. Using data tracing male lineage, the researchers found one line of sires tracing back to the 1880s that was unrelated to Elevation or Chief. That sire was Netherland Prince, born in 1880. A second sire, Colantha’s 2D Sir Henry, is distantly related to Elevation, but splits from that lineage early on. Colantha was born in 1888.
To get semen to start their project, researchers scoured a list of AI bulls descended from Netherland Prince and Colantha. Zimmerman Alstar Pilot, born in 1954, was the Netherland Prince descendant selected. Four sires were matched from Colantha, and U-of-Minn W Caliban Cuthbert was ultimately selected to represent the Colantha line. Cuthbert was actually born in 1989 as part of the University of Minnesota’s long-term control line breeding project, but his sire was born in 1953.
Through invitro fertilization, 12 Colantha lineage embryos and 15 Netherland Prince lineage embryos were obtained. These were implanted in Holstein recipients at Penn State. Three males and 3 females were born to the Colantha lineage while 4 males and 5 females were born to the Netherland Prince line.
The 2 highest genomic Predicted Transmitting Ability for $Net Merit Colantha lineage bulls were enrolled for semen collection at Select Sires when they reached a year of age. Similarly, the 3 highest testing Netherland Price lineage bulls were also enrolled.
Semen from these bulls is now available for further research. Performance of the daughters will also be evaluated to demonstrate the potential of introgressing their long-lost genetic diversity back into the Holstein population, says Dechow. In other words, what’s very old could become new again.