Animal geneticist Harvey D. Blackburn is responsible for collecting and storing
thousands of samples of animal germplasmmainly semen and embryosto
make sure there's enough genetic material to reintroduce a species if necessary.
Much of his collection deals with important livestock such as Holstein cattle
and Yorkshire pigs.
But one of the collections Blackburn, who is the coordinator of the animal
section at ARS's National Center for Genetic
Resources Preservation in Fort Collins, Colorado, is working on is likely not
familiar to many Americans. He is trying to collect 6,000 units of semen from
Navajo-Churro sheep, a breed culturally important to the Navajo tribe of the
The breed was brought to this country 500 years ago by Spanish settlers, and
Navajos have embraced and raised the breed since then. Over time, though, others
convinced the tribe to raise different breeds, so Navajo-Churro numbers are
This project is different from others Blackburn has worked on since the center
accepted its first animal sample in 2000. "It's really a learning experience
for us; it's a step beyond the biology, one in which we have to consider social
implications," he explains.
To develop the collection, animal physiologist Phil Purdy, also of the Fort
Collins center, traveled to the Navajo Nation to collect germplasm from rams
owned by several Navajo sheep producers. Until Purdy developed relationships
with various breeders, there was hesitancy in collaborating with ARS on this
Before 1965, ARS scientists conducted research on the Navajo-Churro and found
that the sheep did well in dry areas; they were able to produce more lambs than
other breeds of sheep. Handspinners like the wool from Churro sheep, and
they are willing to pay premium prices for it. Navajo use the wool to make blankets.
But for industrial wool manufacturers, it has low value.
Blackburn has 1,200 semen samples now from 27 different rams. He hopes to get
samples from at least 50 different males to get a broad sampling of genetic
If there were ever a need to totally regenerate the Navajo-Churro breed from
the ARS collection, a backcrossing strategy could be used. In such a situation,
Churro semen would be used to inseminate a ewe from a different sheep breed.
The resulting offspring would be 50 percent Churro. The process would be repeated
using a female offspring, making the next generation 75 percent Churro. They
keep doing this until the sheep are 93 percent Churro.
The collection could also be used by breeders or researchers to introduce genetic
variation into existing Churro populations.
At one time, there were 2 million of these sheep. In 1977, when conservation
efforts started, there were fewer than 500. Now the estimates are around 1,500.By
David Elstein, Agricultural
Research Service Information Staff.
This research is part of Food Animal Production, an ARS National Program
(#101) described on the World Wide Web at www.nps.ars.usda.gov.
Harvey D. Blackburn and
Phil Purdy are with the USDA-ARS
National Center for Genetic Resources
Preservation, 1111 South Mason St., Fort Collins, CO 80521-4500; phone (970)
495-3268 [Blackburn], (970) 495-3258 [Purdy], fax (970) 221-1427.
"Making Sure Sacred Sheep Don't Become Extinct" was published in the April 2005 issue of Agricultural Research magazine.