In today’s economy your producer clients are looking to save money, reduce costs and make smart economic decisions. Conducting bull breeding soundness exams (BSEs) is still one of the most important ways you can help your clients make wise decisions for their breeding herds.

T.J. Barclay, DVM, Hereford Veterinary Clinic, Hereford, Texas, hasn’t seen clients pull back on their breeding soundness exams because of the economic situation yet, but he says it may happen. “If so, I would ask them to think about the cost of BSEs versus the cost of a poor pregnancy rate due to an infertile bull,” he says.

In times of economic stress, the BSE is more important than ever for herd profitability, adds Dwight Wolfe, DVM, Dipl. ACT, Auburn University. “The goal of the BSE is to identify those bulls that have a high likelihood of getting a significant percentage of healthy cows pregnant in a limited breeding season. Failure to use bulls that are found to be satisfactory potential breeders may reduce first-service conception rates, thereby spreading out calving distribution which ultimately results in less pounds of calf produced.” Coupled with the high cost of maintaining a brood cow, reduced calving percentage of delayed calving with a prolonged calving season can prove economically devastating for breeders.

Other factors can reduce or delay BSEs. Jessica Laurin, DVM, Animal Health Center of Marion County, Marion, Kan., tends to see the number of BSEs influenced by weather and inconvenience issues. “If the weather is poor, then producers do not like to handle the bulls to bring them in for bull testing,” she says. “If they don’t have a handling facility or proper trailers then they tend to bring bulls in less for exams. Sometimes due to weather, they put off bringing bulls in to the point that they end up going straight to pasture instead of getting an appointment to bring them in.”

Laurin says she fails bulls more in February and March than April or May because nutrition and environment influences later sperm production. “A severe winter can depress the BSE in March,” she explains. “The BSE improves by May, and producers understand that, so they tend to put off the BSE, which unfortunately puts them behind the spring bull sales.”

Laurin has also been pushing for more BSEs done at the end of the breeding season. “If a bull tests bad at the end of season, the producer is more encouraged to get the pregnancy testing done more promptly,” she notes. “It can pick out the breeding injuries that the producer has overlooked, and allows for time to correct an issue. It also is more important for the bull that gets used for both fall and spring calving groups.”

Don’t forget morphology

Some great little swimmers can indicate good sperm, but Barclay advises not being satisfied with just that. “I’ve found that there are a lot of practitioners out there who don’t routinely perform morphology exams,” he states. “I’ve had to do quite a bit of explaining to some producers who think that just because the motility is good, then the bull is fertile, but that may not be true.”

Laurin also looks at morphology. In young bulls, a common issue is primary droplets that as the animal matures become secondary droplets, then finally disappear. Misshapen heads, or heads that have fallen off are also common defects that can fail a BSE, especially on a young bull. “Another thing that changes with maturity is that tails get longer with age.  It is not a problem, just an indicator of maturity,” she says.

One thing that has helped Barclay educate owners is a phase-contrast microscope with a video monitor that he uses at his clinic. “When we do a BSE in the clinic, the owner can watch me examine both motility and morphology and I can explain what I’m seeing.” Barclay always follows the Society for Theriogenology guidelines, which call for motility and morphology evaluation. “Some sperm can be morphologically abnormal and incapable of fertilizing an oocyte, but still motile,” he says. “I charge for my time and I believe that the producer is getting more value from a complete exam.”

Failing the BSE

Historically, young bulls failing a BSE most commonly failed to meet the minimum requirements for satisfactory potential breeding in the areas of insufficient scrotal circumference, conformational defects of the feet and legs, or an inadequate percentage of morphologically normal sperm in the ejaculate. “However, by using sires with positive EPD values for scrotal circumference and eliminating bulls that were structurally unsound, a greater percentage of young bulls are now found to be satisfactory potential breeders according to the standards of the Society for Theriogenology,” Wolfe says.

Laurin notes that seminal vesiculitis is becoming a bigger reason for culling young bulls. “We start to see it in 18-month to 2-year old bulls, and it can become a persistent problem with some bulls that will pull them from production at 3–4 years of age.”

The most common reason for Barclay to fail a young (i.e. 1 to 2-year old) bull is sperm morphology, but, “I always recommend a re-evaluation because a lot of those will improve after they’ve matured a bit,” he says.

For older bulls, lameness, penile injuries and degeneration in sperm quality are common reasons for BSE failure. Laurin adds that in older bulls seminal vesiculitis leading to prostatitis and pain on electrical stimulation can occur.

“The more common reason older bulls are not satisfactory potential breeders is inadequate percentage of morphologically normal sperm in the ejaculate,” Wolfe explains. “These bulls frequently have chronic lameness from problems such as arthritis, interdigital fibromas, or chronic laminitis with abnormal hoof growth.”

Regardless of age, Laurin says the bull should be an agile athlete. “Ability to maintain condition is a requirement, and it is important for producers to understand the importance of nutrition and the influence that overfeeding while maturing can harm subsequent physical and reproduction performance.”

Disease and biosecurity

Screening for diseases is dependent on the immediate destiny of the bull, says Wolfe. Bulls may be sampled for Johne’s disease, trichomoniasis, camplyobacteriosis or BVDV depending upon sale or shipping requirements or herd goals and biosecurity plans for the owner.

At the edge of the Flint Hills of Kansas, Laurin says the top three diseases she screens for are BVDV, bovine leukosis and anaplasmosis. “We periodically screen for lepto and trich depending upon age of introduction to the herd or herd health status,” she says.

Barclay will commonly collect samples for trichomoniasis PCR in conjunction with a BSE. “Because we have more producers striving toward BVDV-free herds, PI testing is important for all new bulls,” he adds. Bulls should be vaccinated against IBR, BVDV, leptospirosis and campylobacter regardless of their age, says Wolfe, and he typically recommends that bulls be vaccinated the same as the cow herd they will be used in.

Laurin recommends two modified-live virus (MLV) 5-way vaccinations below one year of age, and one MLV 5-way and vibrio/leptospirosis vaccination between 12–18 months of age. She likes to give a 7-way clostridial at least twice by 12 months of age, then yearly for two years, then every two to three years. “We also vaccinate for tetanus in our area, vibrio/lepto before every breeding season, and depending upon herd status, a 5-way every year to every third year.” She suggests that clients give bulls pinkeye vaccination prior to summer breeding season, and a Fusobacterium vaccination at least once to young bulls, or before breeding season in pastures with endemic footrot.

“Make sure young bulls have had an initial series of vaccinations as recommended by the vaccine manufacturer,” adds Barclay.

Most veterinarians recommend deworming the bulls on the same schedule as the cows. “Bulls need to be able to maintain condition, and thus should be maintained on the same deworming schedule as cows,” notes Barclay. Wolfe adds that for much of the Southeast the optimal timing of deworming is early to mid-summer to minimize pasture contamination.

Both internal and external parasite control are important to optimize breeding performance, states Barclay. “Heavy parasite loads can diminish the overall health of the bull and therefore decrease breeding performance.”

Bull nutrition

Don’t forget about bull body condition through the breeding season. Barclay likes to see a body condition score (BCS) of 5-6 in bulls prior to the breeding season. Poor body condition (either too fat or too thin) will have a negative effect on sperm quality. “In our area, if pasture conditions are adequate, then mineral supplementation is all that’s needed,” Barclay says. “However, in dry conditions or if breeding for fall calving, protein supplementation becomes very important.”

Many bulls tend to lose one body condition score while breeding which may impair their breeding efficiency later in the season. Young bulls usually require more attention to maintain body condition than mature bulls. “Bulls that are excessively fat at the onset of breeding season may have decreased sperm quality compared to bulls in more moderate condition,” Wolfe explains. “Additionally, over-conditioned bulls may lack the athleticism and stamina of bulls that are more fit. On the other side of the coin, bulls that are excessively thin may also have decreased semen quality, libido, and athleticism.”

Laurin looks for a BCS of 4.5-5 at the time of the BSE and, at least 5 at the time of bull let out. “Some producers are better than others at checking BCS toward the end of breeding season,” she says. “A drop in BCS by end of the season can indicate too much activity in the pasture — from either inability to settle cows, to plenty of bull power where cows are settled early in season, or bulls left in too long and not having anything else to do but fight. Bulls should never be fed to be fat, especially in the down season.”

Laurin has seen a few cases of bulls raised with poor nutrition, especially too little protein, and then fail a BSE for lack of a good enough sperm morphology. “The higher the number of cows per individual bull, the more importance placed on providing enough nutrients for ample sperm production.”

Testing AI semen

Laurin wishes she could get more producers to let her look at post-thaw semen quality before the breeding season. She had a producer bring in a tank to check semen quality because he was afraid that the tank had not been maintained properly over the year. “We thawed four straws, each from a different bull. Of the four, three bull straws thawed well, and the semen showed good quality. The fourth showed poor motility after the thaw process.” She would like to see some research looking into the percentage of bull collections that maintain acceptable quality after the freezing and thawing process. “If I have a group that has a poor AI take percentage, it is one area that I am looking into.”

Barclay agrees that testing AI semen post-thawing is not a bad idea, especially if a large number of cows are to be bred with the same batch of frozen semen. “We can easily analyze a drop of semen that’s left in the pipette after insemination if we do it here in the clinic,” he says. “Alternatively, the producer can bring us a straw just for evaluation if he will be doing the inseminations himself.”

Is your equipment in order?

It is important to take care of the equipment, as electroejaculators, microscopes, etc. are expensive to replace. “In our practice, our technicians play a large role in maintaining the equipment, so we make a point of educating new employees on proper cleaning and care,” says Barclay (see care and handling sidebar). “The most vulnerable parts of the electroejaculator are the probe and its cord. You want to always store the cord rolled up neatly to avoid kinks that could result in a short. Also, we’ve cracked a probe by accidentally dropping it on the concrete, so they are not indestructible.”

Laurin likes to have an assistant who stands behind the bull (in a safe fashion such as protected with a sturdy bar or back gate) and keeps hold of the end of the probe, in case it needs to be pulled out or repositioned. 

Laurin says most parts of most units are fairly water resistant, especially the probe.  “We will wash it between bulls in a bucket of water with disinfectant or the sink, to prevent transfer of infectious agents between animals, but the end has to be guarded when washed to prevent damage.”

Having more than one probe at a practice is a good idea. Laurin has noticed that when more than one veterinarian uses a unit, each one handles it differently, and problems can arise with functionality. “In our practice, it is better that each veterinarian has their own unit that they each maintain,” she suggests.

Getting the most out of the probe

Laurin cautions that there are differences in probes. Some provide more electrical stimulation than others, and a user has to be prepared to understand how each one can work well.  She says young bulls tend to perform better with the smaller probe size and less electrical stimulation. “Once a bull is about 4-years old, a larger probe and a hotter probe can work more satisfactorily,” she says.

Technique is important to successful collection. Handling bulls as gently as possible and rectal palpation prior to collection generally leads to easier ejaculation after the probe is stimulated. First time collection on a young bull takes some patience, so introduce electrical stimulation slowly, then speed up as the bull becomes acclimated. “A mature bull can be stimulated quickly and read a hotter setting right away,” says Laurin. “There are times where if a first and second collection in the chute is unsuccessful, it is best to put the bull to the back of the lineup, let it stand for 10-15 minutes, then try collecting again. Also, a full bladder will provide difficulty in getting satisfactory stimulation, so putting the bull through the chute again can be beneficial by allowing it time to urinate.” 

Dairy bull BSEs

There are still a lot of dairy bulls in use on dairies, and they need breeding soundness exams, too. However, as of a few years ago, less than 10% of dairy clients (based on two different surveys of producers) had ever had BSEs performed on their bulls, says Mike Overton, DVM, MPVM, University of Georgia. “BSEs are a vastly underutilized screening tool and unfortunately, due to the  current, tough financial times, it seems unlikely that we will convince more dairy owners to begin using this tool.”

When he does perform BSEs, Overton says, “The single most common reason for failure in my hands for Holstein bulls is related to testicular or seminal vesicle issues??—??inadequate scrotal circumference, infections resulting in white blood cells in the semen, testicular injuries, testicular hypoplasia, etc. The second most common category of reasons was sperm morphology and the third was actually lameness or other disease issue.”

Dairy bulls aren’t kept around as long as beef bulls. Overton says they’ll start using them at about 15-months of age, and then they are usually culled no more than 12 months later.

Dairy bull health protocols

Overton offers this hypothetical vaccine schedule as an example of a dairy bull vaccination protocol:

At 12–13 months of age, IBR, BVDV, BRSV, PI3. Overton prefers modified live virus (MLV) and a cytopathic virus vaccine to reduce the risk of persisently-infected testicles that may result from use of noncytopathic vaccine. Bull are also given a leptospirosis hardjo-bovis and 5-way vaccine, a double dose of vibrio and a 7-way clostridial.

At 13–14 months, bulls are given IBR, BVDV, BRSV, PI3 (cytopathic and MLV). Bulls are also given a leptospirosis hardjo-bovis and 5-way vaccine, a double dose of vibrio and a 7-way clostridial.

At 20-months of age bulls are given another dose of vibrio and a leptospirosis hardjo-bovis plus a 5-way vaccine.

As far as internal parasites, Overton notes that in the Southeast, it’s primarily important to be aware of Ostertagia issues.

Dairy bull nutrition

Dairy bulls should be introduced at a body condition score (BCS) of about 2.5 to no more than 3.0 on a 1 to 5 scale, Overton suggests. Dairy bulls will definitely gain weight while in the breeding pens since they are consuming the lactating diet.

“Fat bulls are usually lazy with a reduced libido and more susceptible to the effects of heat stress,” says Overton, and there can be issues with overfeeding protein, energy and calcium since they are eating the same ration as the cows. Because of this, Overton recommends a rotational management system for dairy bulls.

Care and handling of eletroejaculators

Electroejaculators are an expensive piece of equipment often used in rugged conditions. Neogen offers these tips for the care and handling of electroejaculators. While this information is specific to the ElectroJac 5, the basic care and handling guidelines apply to any electroejaculator.


  • Make sure the battery is connected properly.
  • Do not lay the probe on anything metallic when it is connected to the electronics. Doing so could short the electrodes and may blow the fuse or possibly damage the electronics.
  • Keep probe away from water and water pressure. 
  • Keep the electronics away from water. The electronics instrument case is not waterproof. Water can damage the unit’s electronics.
  • Be careful when handling the dwell box. The on/off switch and the dwell switch can be damaged when the box is not handled with care.
  • Hold the bull’s tail down to prevent the probe from slipping out and falling to the ground.
  • Contact the manufacturer’s customer service for assistance if the animal appears to be experiencing undue distress while using the equipment.
  • Do not attempt to alter or repair the electrojaculator. Contact  manufacturer’s customer service for all maintenance and repair matters.
  • Make sure that the bull is disconnected from the unit and probe before opening the chute.

Usage Suggestions for electroejaculators

  • Immobilize the bull Use a headgate and squeeze chute, or similar solid enclosure, to limit the side-to-side and forward and backward motion of the bull. Bulls with room to move are more likely to fall, making collections more difficult.
  • Footing is critical Providing secure footing is perhaps the most important aspect of preparing a bull for collection. Bulls that are slipping and sliding are difficult to collect. Some veterinarians spread a bucket of sand over the enclosure’s floor to increase a bull’s footing, and others have bulls stand in ankle-deep sand to insure stable footing.
  • Pre-stimulate the bull Manually pre-stimulating the bull by gently massaging the prostate and ampullae for 10-15 seconds prior to inserting the probe can relax the animal, and shorten the collection time.
  • Try automatic mode first Veterinarians have found that up to 90% of bulls can be quickly collected using an electroejaculator’s automatic mode if available. Manual mode is most useful with older bulls that are more difficult to stimulate.
  • Charging the battery Check the suggested charging information for the electroejaculator you are using.

Beef bulls by the numbers

The National Animal Health Monitoring Service (NAHMS) recently released Beef 2007–2008 study indicates that the most common breeding method used by cow-calf producers is “natural service” by a bull only. For breeding, most heifers (79.2%) and cows (94.2%) were only exposed to a bull (as opposed to AI). Cow-calf producers expected mature bulls to service 25 females and yearling bulls to service 17 females. Most reproductive specialists advocate that a mature bull can service 25 to 35 cows; however it has been shown that highly fertile bulls can service up to 50 cows.

Breeding soundness exams

The percentage of operations that tested the semen of at least some bulls in preparation for the last breeding season ranged from 18.1% of operations with 1 to 49 beef cows to 61.1% of operations with 200 or more beef cows. A lower percentage of operations with 1 to 49 cows performed scrotal measurements in preparation for the last breeding season than did larger operations. Of the 30.7% of operations that purchased, leased, or borrowed bulls for the last breeding season, 71.3% semen tested at least some of these bulls.

Only 9.8% of operations cultured bulls for Tritrichomonas fetus, and just 18.5% of bulls were cultured for T. fetus in preparation for the last breeding season; 35.1% of operations that purchased, leased, or borrowed bulls in preparation for the last breeding season cultured bulls. Additionally, 53.3% of operations that purchased, leased, or borrowed a bull, added bulls that were more than 18 months of age or no longer considered virgin, but only 34.4% of those operations cultured all these bulls for T. fetus.