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% 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 16-19% 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 cm.