Bulls play a crucial role in the success of a breeding program, yet their management is often overlooked. Proactive care year-round is essential, as it directly impacts their performance during the breeding season. One of the most important components of bull management is the breeding soundness exam (BSE), which serves as the foundation for effective fertility management. All bulls, including yearlings, newly acquired animals, borrowed, and resident bulls, should undergo a BSE before each breeding season. It’s important to remember that passing a BSE in one year does not guarantee future success in subsequent seasons. For operations with both spring and fall breeding seasons, bulls should be tested twice a year, prior to each season.
A BSE assesses more than just semen quality; it also includes evaluations of physical soundness, and scrotal circumference. According to the USDA report, the percentage of operations that checked purchased, leased, or borrowed bulls was 67%; however, only 31% of operations tested resident bulls. This oversight can lead to decreased fertility and potential financial losses. In a study evaluating the impact of BSE on reproductive efficiency, researchers divided a group of bulls into two groups. Group 1 underwent a BSE, and only bulls that passed the exam were exposed to cows. Group 2, however, had bulls exposed to cows without any testing. The study found that cows exposed to bulls that passed the BSE had at least a 5% higher pregnancy rate compared to those exposed to untested bulls. This highlights the importance of testing bulls prior to the breeding season.
It’s important to note that in this study, cows were exposed to multi-sire pastures, meaning bulls with both good and poor semen quality were mixed together in Group 2. In cases of single-sire pastures (moist Tennessee producers), the difference in pregnancy rates between bulls that pass or fail a BSE may be even more pronounced.
Nutritional Status
Nutrition plays a critical role in bull fertility. Bulls should begin the breeding season with a body condition score (BCS) between 5.5 and 6.5. For younger bulls (under 24 months), aiming for a BCS closer to 6.5 is recommended, as they are still in the growth phase. Bulls commonly lose up to one full body condition score during a 60- to 90-day breeding season, which translates to a weight loss of 100 to 200 pounds. Producers should closely monitor body condition throughout the breeding season and remove any bull that experiences significant weight loss until he can regain a healthier score.
Injury and Its Implications
Injuries can have a significant impact on a bull’s fertility. Lameness affects both movement and the ability to mount females, and even with acceptable semen quality, an injured bull cannot breed effectively. Injuries to the penis or prepuce can impair intromission, reducing the bull’s ability to mate. Bulls also rely on their vision to locate sexually active groups of females (SAGs), so severe eye injuries resulting in blindness can cause a bull to fail a breeding soundness exam (BSE). Additionally, injuries to the scrotum and testes can lead to reduced fertility or even infertility (in cold weather, it could cause frostbite and impair thermoregulation). Therefore, closely monitoring both the cow herd and bulls during the breeding season is essential to ensure the bull remains physically sound for breeding throughout the season.
Libido and Social Hierarchy
Another important factor not included in a BSE is libido. Since libido is difficult to measure directly, the best management practice is to observe the bull’s behavior during breeding. After passing a BSE and being turned out with cows, monitor the bull to ensure he shows interest in breeding.
When multiple bulls are placed in the same pasture, consider their size and age. Older, larger bulls typically dominate younger, smaller ones, establishing a social hierarchy through fighting. Therefore, when mixing bulls, be vigilant for fighting injuries. Whenever possible, separate younger bulls from older ones to minimize conflicts. Even if a hierarchy is established within the cow herd, bulls will re-establish their dominance when moved to different pens or pastures, often leading to increased fighting.
Off-Season Management Strategies
Research on managing and maintaining bulls during the off-season is limited, yet it is crucial for the success of beef operations, as bulls are vital assets found on most, if not all, beef farms. Many operations define their breeding seasons as lasting less than 150 days, meaning that for most of the year, these valuable animals are housed separately from the rest of the herd. Effectively managing bulls during this period is essential to ensure they remain sound, healthy, and capable of passing a breeding soundness exam (BSE) for the next season. Identifying bulls that are less likely to pass a BSE and promptly assessing their salvage value is equally important.
During the off-season, efforts should focus on helping bulls recover lost condition, targeting a body condition score (BCS) of 5.5 to 6.5. Remember that spermatogenesis — the process of sperm production — takes approximately 60 days in bulls, so they should be in optimal condition at least 60 days before the breeding season begins. Providing ample exercise is also important; positioning the feeding bunk and water trough at opposite ends of the pen encourages movement.
Herd health management should not be overlooked during the off-season. Implement all possible health measures at least 60 days prior to breeding. Vaccination protocols for bulls should align with those for the cow herd, and consulting a local veterinarian — who understands regional disease risks — is key to determining the best vaccination strategies for both bulls and cows. Additionally, parasite control for bulls should mirror the approach taken with the cow herd. Testing bulls for BVD-PI, Anaplasmosis, Trichomoniasis, and Campylobacter (Vibrio), especially when purchasing or borrowing bulls, is an effective strategy to prevent potential outbreaks within your herd.
Summary
In summary, effective bull management is essential for maximizing breeding success in beef operations. Regular breeding soundness exams (BSE), proper nutrition, and attention to injuries and libido are key to enhancing fertility. Additionally, off-season practices such as monitoring body condition, implementing vaccination protocols, and ensuring adequate exercise are vital. By adopting a comprehensive management strategy, beef producers can protect their investments, boost reproductive performance, and increase overall profitability.
Source : tennessee.edu