Bull Fertility Tests: An Industry Collaboration

Enhance Economic Opportunities for Agricultural Producers
Research Year: 

Fertility in a livestock enterprise is 5 to10 times more important economically than any other production measure. Cows bred to high-fertility bulls bear more calves earlier in the season, resulting in more beef weaned and marketed per cow, which is a direct measure of profit. Bulls with identical semen quality in terms of physical assessment vary in actual fertility. Means to identify bulls on the basis of fertility potential could result in higher pregnancy rates, leading to larger calf crops.

Description of Action: 

During the 1990s University of Arizona animal scientists assisted in developing a color-based diagnostic test to identify a protein on bull sperm. An antibody is used to detect presence or absence of that protein which is referred to as fertility associated antigen (FAA). Bulls with FAA on their sperm are 17 percent more fertile than herdmates lacking FAA over a 60-day breeding season. Heifers inseminated once to bulls with sperm-associated FAA had a 16 percent higher pregnancy rate than herdmates inseminated to bulls without FAA on their sperm. The original diagnostic test, released for commercial use in 1998, was licensed for any rancher or veterinarian in the world to use. Since then it has been adopted by breeders across the U.S., and in at least a dozen countries worldwide, in the Pacific Rim, South America, Canada and Europe.

In January, 2004, the next generation of that test, a lateral-flow cassette containing reagents to detect FAA, entered the market after University of Arizona scientists conducted extensive research on it. It takes 20 minutes to run and works just like a pregnancy test that can be conducted a home: a purple line in the cassette window indicates the presence of FAA. More than 900 bulls from 19 herds were screened with the new test by UA Department of Animal Sciences researchers who traveled to six states during spring, 2003. Of the bulls tested, 25 percent were found to be FAA-negative. In comparison trials employing artificial insemination, bulls determined to be FAA-positive were 18 percent higher in fertility than herdmates deemed to be FAA-negative. Thus, the fertility differences are the same as the original test.

This work was sponsored by a USDA Small Business Innovative Research grant to ReproTec, Inc., the company in Tucson that markets the test. They hold an exclusive license to offer this test worldwide; the UA held a subcontract on the project. UA scientists are now screening for mutations in the FAA gene that may serve as a DNA-based diagnostic test. TMI Laboratories International, LLC in Tucson is funding the research with the technology licensed to them from the UA’s Office of Technology Transfer.


Detecting high fertility bulls is the key to increasing livestock production and thus profitability. The new bull fertility test is not only accurate, it’s also user-friendly, faster than the previous two-day laboratory method, and cost-effective. Housed in a small plastic cassette about the size of a stick of chewing gum, it has a three-year shelf life, requires no special storage, and can be used chute-side with results in about 20 minutes. If a few tests are purchased at $45, at a $50 profit per calf, and if a bull remains in a herd for four years breeding 25 cows per year, the return on investment is 13-fold per each cow bred. For bulls, a $45 test yields a net return of $140 per bull tested. If the kits are ordered in large batches to cut the cost to $30 per test, using the same inputs stated above, then the return on investment becomes 22-fold per cow.

A 1 percent increase in fertility in the U.S. beef industry would return a net profit of $55-60 million to U.S. producers. Obviously, on a global scale, billions of dollars of income could result from identifying higher fertility bulls and males of other livestock species. On a local scale, an Arizona rancher who bred FAA-positive bulls to heifers in a higher ratio than usual–one bull to 20 heifers instead of the industry standard rate of one bull to 15 heifers–found that he got the same 92-95 percent pregnancy rate during the first 45 days while using a third fewer bulls and no additional feed.

Funding Agencies: 

Hatch Act, National Research Initiative; Sire Power, Inc. and King Ranch; USDA Small Business Innovative Research grant; TMI Laboratories International, LLC

Conact Name: 
Roy L. Ax
Contact E-mail: 
Contact Address: 

Department of Animal Sciences

P.O. Box 210038

The University of Arizona

Tucson, AZ 85721-0038

Tel: (520) 626-2907, FAX: (520) 621-9435