Sheep graze near a mountain lake at the U.S. Sheep Experiment Station in southwestern Montana. Click the image for more information about it.

To Boost Flock Fertility, First Find Superior Studs

By Erin Peabody
August 23, 2005

Sheep producers expect a lot from the rams in their flocks. Many depend on just one of these male sheep to mate with every 20 of their ewes. So if the males aren't up to the task, new rams--often costing upwards of $500--must be brought in.

To help producers get more breeding for their buck, animal scientists with the Agricultural Research Service in Dubois, Idaho, have determined the simplest and most effective way to increase these rams' reproductive potential.

Instead of trying to find the source of trouble--males with languishing libidos--the researchers discovered it's easier to just identify the best breeders, or the sheep that are most sexually active.

Animal scientists John Stellflug and Gregory Lewis of the agency's U.S. Sheep Experiment Station in Dubois, recently completed their most extensive study on the problem of low sexual performance in rams.

Using about 1,000 ewes and 15 rams, the two researchers wanted to find out which of the tests currently used by the industry is most accurate for predicting mating performance. They even used the latest molecular genetics technology--including a sheep "paternity test"--to confirm which rams had impregnated the most ewes and sired the most lambs.

The researchers confirmed that serving-capacity tests, which have been used for at least three decades, are a simple and effective way to identify promising performers. For these tests, producers document how many times a ram attempts to mate when exposed to female sheep in estrous.

For a relatively small investment in time and money, this approach allows producers to spot which of their animals are "high-performance" rams. Stellflug and Lewis calculate that producers could cut the number of rams needed by half, if they were to identify the most promising breeders through screening techniques such as the serving-capacity test.

The Dubois researchers are now conducting experiments to further streamline the serving-capacity test for easier use by breeders who raise and sell rams to sheep producers.

ARS is the U.S. Department of Agriculture's chief scientific research agency.