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CORVALLIS - A new poultry sperm assay developed by scientists at Oregon State University should significantly improve production efficiency and the management of male poultry in commercial breeding flocks.

The assay measures how well sperm swim, and can identify roosters and tom turkeys that would make superior breeders.

"Sperm mobility is essential if the sperm cell is to function as a self-propelled DNA delivery vehicle," said David Froman, an OSU associate professor of animal science.

"In the past, semen evaluation identified the losers," he said. "Our new assay picks the winners. So now instead of throwing out the losers Ñ and there are a lot of them Ñ breeders can pick out a relatively small number of highly fertile males."

In less fertile roosters, sperm aren't mobile enough to get to sperm storage tubules in the hen's lower oviduct. If they don't swim that far, they'll never get to the site of fertilization, which is the uppermost part of the oviduct.

"Those sperm don't even die trying," Froman said. "They're toast."

OSU Agricultural Experiment Station scientists "stumbled onto the assay" as they were trying to find out why a particular line of roosters was sub-fertile. What the researchers found was that these roosters' sperm were notoriously poor swimmers.

Froman's doctoral student, Derek McLean, and research associate Allen Feltman screened 100 roosters and compared the birds' sperm mobility. The hatchability of eggs from hens inseminated with highly mobile sperm was 10 percent greater than hatchability of eggs inseminated with sperm having average mobility.

"Our assay simulates the challenge poultry sperm face immediately after insemination Ñ namely, that they must swim a distance of several centimeters and enter the sperm storage tubules," Froman said.

He said the difference between non-mobile and mobile sperm was much the same as a salmon lolling in calm water versus one that swam vigorously upstream.

"Until now, there had never been a good way to pick the winner among roosters and tom turkeys," Froman said. "This is especially important in artificial insemination, because only a few males are needed to fertilize hundreds of females."

A slightly modified version of the OSU assay, which Froman described as "practical and fast," is being used by USDA Agricultural Research Service scientists in Beltsville, Md., to test reproductive potential of turkeys.

"We are finding tremendous variability among males," Froman said, noting that using just the best males would considerably improve poultry production efficiency.