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Eddie Baggs: Evaluate bull fertility for best breeding results

With the 2011 Denton County calf crop estimated to be more than 23,000 head, and the beef cattle market at an all-time high, this might be an ideal time to evaluate bull breeding soundness.

Research suggests bulls that are evaluated and found satisfactory have a 6 percent higher fertility advantage.

A good bull that is fertile and an active breeder may sire 80 or more calves, where as a less fertile bull may sire only a few or none. However, most producers do not push their bulls to sire 80 calves. The average ratio of bulls to cows is 1 to 25 for mature bulls and 1 to 17 for yearlings; nonetheless, fertility is still important to sustain an annual calf crop.

A new reproductive test that detects a protein in bull semen, called “fertility associated antigen” or FAA, will help identify superior fertile bulls. Bulls that test positive for FAA are 16 percent to 19 percent more fertile than those testing negative for the protein.

Another fertility indicator is scrotal circumference, which directly relates to both volume of semen and percent normal sperm cells. Research has also shown a strong genetic relationship between scrotal circumference in bulls and the fertility of his daughters. The recommended scrotal circumference for a bull one year of age is 30 centimeters.

Sex drive or libido is also a part of bull fertility. Bulls that lack libido will exhibit signs of shy breeding, and may also include fighting and bonding with one particular cow while ignoring others in heat. Such bulls sire fewer calves and are economic liabilities to cow-calf producers.

Besides fertility, other traits should be taken into consideration when evaluating breeding capabilities, such as structural soundness, growth, calving ease, frame size and maternal performance. Highly fertile bulls will breed some cows earlier in the breeding season and will result with increased weaning weights of older calves. With this in mind, and based on a 6 percent increase in calving percentage coupled with today’s cattle market prices, the return on a breeding soundness exam would be a wise investment.

Working calves before sale will also increase profits. This might include vaccinating, deworming, implanting, castration and dehorning, with castration adding the most value to calves at 5 percent over non-castrated bull calves.

These and other value-added options can be found at


EDDIE BAGGS, extension agent with the Texas AgriLife Extension Service in Denton County, can be reached at 940-349-2880.