Testosterone test spots dud studs - Science Update - Brief Article

Agricultural Research, Oct, 2002

Since 15 to 25 percent of male sheep in U.S. flocks don't mate, ranchers want to find a way to identify good breeding rams. Just one nonbreeder can cost up to $500 to buy and maintain--not to mention the lost potential of lambs not born. Some producers use artificial insemination to sidestep the problem of variable male libidos, but that means more labor costs. Others rely on multiple-sire breeding groups to make sure all ewes get bred. But this practice incurs extra sire costs and makes it impossible to know resulting lambs' paternity.

A new test, based on the premise that libido and testosterone secretion are closely linked, may take the guesswork out of ram purchase. It uses an injection of naloxone to block certain hormones and stimulate testosterone release. The testosterone response of male mammals given naloxone predicts whether or not they will be sexually active.

Ranchers could use the test to save both time and money and increase the reproductive potential of their flocks. This technology has been patented and is now available for licensing. John N. Stellflug, U.S. Sheep Experiment Station, Dubois, Idaho; phone (208) 374-5306, e-mail tellflug@dcdi.net.