From Beef Cow Calf Weekly

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New Chute-Side Test Identifies Higher Bull Fertility "Even in rough country with otherwise reproductively fit bulls, research proves the absence or presence of a heparin-binding protein, dubbed fertility-associated antigen (FAA), can make a world of difference in terms of how many cows a bull settles within the first 60 days of the breeding season," Wes Ishmael writes in the November issue of BEEF.

Roy Ax, a University of Arizona (UA) animal scientist and researcher, says sperm can't penetrate an egg's protective coating to allow fertilization until the sperm is activated through a process termed capacitation. Capacitation occurs when the acrosome -- a region located on the head of the sperm -- swells and bursts to release enzymes that allow egg penetration (an acrosome reaction). This process occurs in the reproductive tract of the cow over the course of six to eight hours after the semen is deposited there.

Ax discovered that the presence of FAA enables increased acrosomal reaction. Thus, if FAA is present, capacitation of more sperm in the semen occurs, which means more sperm have the opportunity to fertilize the egg.

Ax and fellow researchers developed a test to accurately identify bulls positive and negative for FAA. They then began to compare the fertility of bulls positive for FAA to those negative for the protein.

Thus far in the study, a total of 304 bulls positive for FAA have been bred to 8,281 cows, while a total of 217 FAA-negative bulls have been bred to 5,167 cows. The positive bulls have settled 16.1% more cows within the first 60 days than FAA-negative bulls (78.6% for FAA-positive and 62.5% for FAA-negative). The study includes bulls from a cross section of breeds.

"Selecting bulls with FAA present in sperm membranes, compared to bulls without, results in about five more calves per 25 cows exposed to a bull," says Ax. "If selection of bulls with FAA resulted in only one additional calf weaned per herd, the national economic impact to producers would be $19.2 million."

Other benefits include being able to reduce the size of a bull battery and still get as much conception. Those savings put a producer in a position to buy better bulls.

To see the entire story, go to <A HREF="" TARGET="_blank"></A> and click on "Bull Booster." For still more on breeding topics, go to <A HREF="" TARGET="_blank"></A> , a research archive site from BEEF magazine devoted exclusively to cow-calf production and management topics. Click on "Bull Management" or "Breeding and Genetics" in the opening-page menu, or enter a subject in the "Search Titles" box. -- Joe Roybal

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