News Release
January 26, 2009

UW, USDA research should enable sheep producers to easily improve genetics

Research by the U.S. Department of Agriculture (USDA) and University of Wyoming College of Agriculture should enable sheep producers to more easily, and cost effectively, improve genetics of their flocks.

The two-fold project focuses on semen collection/storage and an inexpensive yet effective method to artificially inseminate ewes.

“The availability of a cost-effective AI (artificial insemination) procedure would facilitate and enhance genetic programs for sheep,” said Bob Stobart, an associate professor in the UW College of Agriculture’s Department of Animal Science and a sheep/wool specialist with the UW Cooperative Extension Service.

“It will really assist in getting higher quality genetics throughout the United States,” he said.

Stobart presented the research at the American Sheep Industry Association’s annual convention Jan. 21-24 in San Diego.

The team’s lead scientist is Phil Purdy, an animal physiologist with the USDA Agricultural Research Service’s National Animal Germplasm Program (NAGP) in Fort Collins, Colo.

Collaborators on the project are Stobart, Brent Larson, manager of the UW College of Agriculture’s Sheep Unit west of Laramie, and Harvey Blackburn, an animal geneticist with the NAGP.

Phase one of the research revealed semen can be collected and held at 41 degrees Fahrenheit for up to 48 hours prior to cryopreserving without impacting sperm quality. Cryopreservation maintains the viability of semen by storing it at very low temperatures.

Purdy said this finding is important because it will allow sheep producers to perform collections on their ranch and then “overnight ship” the semen to distant laboratories for storage. It will also improve research potential at facilities such as the NAGP, he said.

The team is now in the final stages of part two of the research, which is exploring an alternative method of non-surgical AI.

To date, Stobart said, non-surgical techniques have not been consistently successful because ewes have a cervix that is difficult to access because of folds within the cervix, unlike cattle, which have a cervix that can be physically manipulated.

Stobart said a surgical method to AI ewes, which involves the use of a laparoscope (a slender surgical device that is inserted through a small incision in the abdominal cavity), has produced the best results, but the procedure requires a high level of expertise to achieve acceptable levels of fertility. Also, this method is very expensive, costing $40 to $50 per head. Because of this, Stobart said, few producers use this technology. Instead, they turn rams loose with ewes, but this doesn’t give producers the option to improve genetics by artificially inseminating ewes using stored semen from other rams.

 “We’re using a small device that works its way through the folds of a ewe’s cervix,” Stobart said. “It’s a fairly simple and straightforward method that could be done by producers on the farm.”

Stobart said good results have been obtained with test animals, but now they are trying to develop a way to determine when ewes are cycling naturally so good AI results can be achieved with large flocks at a ranch or farm.

A promising method involves using a “marker ram” equipped with a harness on its chest containing a block of chalk.

“A ewe won’t let a ram mount her until she is cycling,” said Stobart, who noted the method being tested would allow producers to regularly check their flocks and pick out ewes having chalk on their backsides. The chalk indicates they are cycling and could be artificially inseminated.

Marker rams receive vasectomies prior to being placed in pens so they don’t impregnate ewes.

“This method is much less labor intensive and expensive than laparoscopic surgery, it’s non-invasive and we believe it would allow any producer to AI their ewes,” Stobart said.

The team is now fine-tuning the technique in order to increase fertility rates.

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Contact: Robert Waggener, Editor
Phone: (307) 766-3571
E-mail: robertw@uwyo.edu

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