What’s in a breeding soundness exam?

It’s that time of year again when cattle are itching to graze fresh new pastures and young calves have a newfound freedom running through green grass. Soon herd bulls will find their place with the cow herd and breeding season will begin – starting a new cow-calf production cycle. Yet before turning out sires, it’s important you make sure bulls will be able to do their job effectively by conducting breeding soundness and health exams to ensure a successful breeding season.

Taylor Grussing

Client Experience Manager / Vytelle

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Breeding soundness examinations (BSE) first began in the 1940s and continued to evolve for 50 years until the current standards were set in the 1990s. Today’s BSE include a physical exam (internal and external genitalia), scrotal circumference and semen sample, which is evaluated for motility and morphology.

Pre-breeding season BSE should be conducted 30 to 60 days prior to the beginning of the breeding season in order to allow time for re-testing, if necessary. BSE forms utilize a pass/fail method for each part of the exam in order to determine if bulls will be able to service cows.

Physical exams begin with evaluating the health, body condition and conformation of the bull. This addresses questions such as: Is his vision adequate to allow him to see cows that need to be bred? Is he structurally sound, allowing mounting and mobility around the pasture? Can he maintain his body condition (is he too fat or too thin)?

In addition, the physical exam includes palpation of internal and external genitalia for abnormal adhesions, inflammation or abscesses that may impact his breeding ability or spread disease.

This section of the exam is just as important as the semen evaluation because if a bull cannot see or smell cows in heat, move around the pasture or maintain his body condition, then he’s likely not the bull you want servicing your cows.

One note to remember is that BSEs do not measure libido. Therefore, bulls should be observed in a breeding environment to ensure the desire is there and that he can fully insert and complete the breeding process. If he can’t service cows, then a replacement should be found.

Scrotal circumference is an indicator of puberty and is utilized in a BSE to set a minimum size that must be reached by a certain age (regardless of the breed) to pass a BSE. For example, yearling bulls must measure 30 centimeters and 2-year-old bulls must be 34 centimeters at exam time to pass.

Other countries have made changes to scrotal circumference requirements based on breed difference, but these have not been noted in the U.S. yet.

Motility is a measure to evaluate the forward movement of the semen sample as a group (gross) and individually. Gross motility motion evaluations include rapid swirling, which rates very good and receives 70 percent individual rating. Moreover, generalized oscillation rates as fair and receives a 30 to 49 percent individual motility. Concentration is not evaluated in a BSE. In order to pass the motility section of a BSE, a minimum of 30 percent progressively motile sperm must be observed. While this percentage seems low, differences in semen handling (processing and temperature) play a large role in the variation between samples and evaluators; thus the passing rate was adjusted to account for these major differences.

Morphology is an evaluation of the size, shape and development of the sperm cells (where 70 percent minimum normal cells are needed to pass).

For this reason, morphology is commonly the section of a BSE where most bulls fail. During the morphology section of the exam, sperm cells are counted and classified into “primary versus secondary” abnormalities categories. Primary abnormalities typically occur during spermatogenesis in the testicle. Secondary abnormalities arise from altered maturation in the epididymis. Which category the abnormal sperm cells fall into will help determine re-test time.

Final BSE results

After all sections of a BSE are conducted, bulls are classified as a satisfactory potential breeder – if they pass the physical exam and all minimum requirements of the semen evaluation. Unsatisfactory potential breeders are ones that do not meet either one of the physical exams or fail to meet several of the minimum BSE value.

Lastly, bulls that fail to meet one minimum section of the BSE are classified as “classification deferred” and can be re-tested at a later date.

Remember, a BSE is not good for life. A passing score means that bull is fertile that day, but physical and environmental injury, disease or fever could affect future fertility. Keep watch of bulls during the breeding season and consult with your veterinarian to re-test as necessary.

Reproductive diseases

All bulls should pass a BSE prior to breeding season, but non-virgin bulls that may be moving between herds should also be tested for reproductive diseases such as vibriosis and bovine trichomoniasis or “trich.” This past year, trich made a resurgence in several areas of the country.

Trich is a venereal disease caused by a protozoal organism that lives in the sheath of a bull and can be passed to a female through the act of mating.

Once infected, the organism will cause inflammation of the female reproductive tract that result in the loss of a pregnancy. Bulls remain positive for life and should be eliminated from the herd. To determine if an exposed bull may have trich, a swab of the sheath can be taken by a veterinarian and submitted to a lab for evaluation.

If, at pregnancy check time, an uncommon number of cows are determined to be open or a large number of cows are bred late in the season, this may be cause to test the exposed bull battery for a trich infection.

Summary

At the end of the day, a bull’s job is to get cows pregnant and proper management of fertility, health and nutrition are key areas producers need to focus on to aid in his success during the breeding season. Don’t cut costs on bull management or BSEs as, long-term, this decision will affect profitably and longevity of the operation.

Consult with your herd veterinarian, seedstock supplier and nutritionist and livestock specialists for assistance in preparing bulls for the breeding season.