One key to potential profitability in the cow/calf beef operation is maintaining a herd where the cow has a calf each year. As calving interval increases above 13 months and cow pregnancy rate drops below 90%, profit potential decreases significantly. Attention to cow health and condition are important to achieve these goals, but do not forget about the bull(s). Just about every year there are stories of low herd pregnancy rates that are traced back to the bull. Work with your veterinarian to schedule a breeding soundness exam. The following article about breeding soundness exams written by Glen Selk from Oklahoma State University is taken from a 2018 Beef Cattle Letter posting.
“For the breeding soundness evaluation to be successful, bulls should be evaluated 30 to 60 days before the start of breeding. It is important to allow sufficient time to replace questionable bulls. A breeding soundness exam is administered by a veterinarian and includes a physical examination (feet, legs, eyes, teeth, flesh cover, scrotal size and shape), an internal and external examination of the reproductive tract, and semen evaluation for sperm cell motility and normality.
The physical examination studies overall appearance. Flesh cover is one factor to evaluate. Body condition can be affected by length of the breeding season, grazing and supplemental feeding conditions, number of cows the bull is expected to service and distance required to travel during breeding. Ideally, bulls should have enough fat cover at the start of breeding so their ribs appear smooth across their sides. A body condition score 6 (where 1 = emaciated and 9 = very obese) is the target body condition prior to the breeding season.
Sound feet and legs are very important because if they are unsound, this can result in the inability to travel and mount for mating. The general health of the bull is critical since sick, aged and injured bulls are less likely to mate and usually have lower semen quality. The external examination of the reproductive tract includes evaluation of the testes, spermatic cords and epididymis. Scrotal circumference is an important measure that is directly related to the total mass of sperm producing tissue, sperm cell normality and the onset of puberty in the bull. Bulls with large circumference will produce more sperm with higher normality and reach sexual maturity sooner.
Examination of the external underline before and during semen collection will detect any inflammation, foreskin adhesions, warts, abscesses and penile deviations. The internal examination is conducted to detect any abnormalities in the internal reproductive organs. Ask your veterinarian about the need to test the bulls for the reproductive disease, trichomoniasis. Learn more about this disease by downloading and reading OSU Fact Sheet VTMD-9134 “Bovine Trichomoniasis”.
The semen evaluation is done by examining a sample of the semen under a microscope. The veterinarian will estimate the percentage of sperm cells that are moving in a forward direction. This estimate is called “motility”. In addition, the sperm cells will be individually examined for proper shape or “morphology”. Less than 30 percent of the cells should be found to have an abnormal shape.
Any bull meeting all minimum standards for the physical exam, scrotal size and semen quality will be classed as a “satisfactory” potential breeder. Many bulls that fail any minimum standard will be given a rating of “classification deferred.” This rating indicates that the bull will need another test to confirm status. Retest mature bulls after four to six weeks. Mature bulls are classified as unsatisfactory potential breeders if they fail subsequent tests. Young bulls that are just reaching puberty may be rated as “classification deferred”, and then later meet all of the minimum standards. Therefore, exercise caution when making culling decisions based on just one breeding soundness exam.
Many producers work hard to manage their cows for high fertility. They may assume that the bulls will do their expected duties. However, it’s important to pay close attention to bulls to establish successful breeding.”
Rory Lewandowski is an OSU Extension Agriculture & Natural Resources Educator and may be reached at 330-264-8722.
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