During the past 2 decades, competitive bull riding has transitioned from just one of the events in a traditional rodeo to a stand-alone multimillion-dollar sporting event with an international following.1 With the rising popularity of the sport, the bulls involved have emerged as featured athletes with large followings on social media, and champion bulls can generate several hundred thousand dollars in prize money.
Bull riding is a timed and judged event in which a rider attempts to ride a bull out of a chute into an arena and remain atop the bull for 8 seconds. During the ride, a bull rider holds onto a bull rope, which encircles the heart girth of the bull directly behind the thoracic limbs and is weighted with a metal bell so that it will fall off the bull as soon the rider is bucked off or dismounts the animal. Additionally, a flank rope, or strap, is applied around the flank of the bull to facilitate bucking; it is designed for quick release and is removed immediately after the bull exits the arena. Bulls are usually allowed a walk-through of the arena prior to each event, similar to a pregame warm-up for human athletes, and many bulls are trained to stop bucking when a whistle blows after 8 seconds.2 A successful ride, or cover, is achieved when the rider remains atop the bull without any disqualifications for 8 seconds. Each ride is assessed by a panel of judges who award points in 5 categories (buck [how high the bull gets into the air], kick [extension of the bull's pelvic limbs at the peak of each jump], spin [extent of turning and revolutions made by the bull], intensity [the amount of effort the bull puts into the ride], and degree of difficulty [determined by the bucking characteristics of the bull as well as a combination of the other 4 categories]).3 Those criteria are scored individually by each judge, and the mean is calculated to determine the score for the bull.3 For each ride, the maximum mean score possible for a bull is 50 points. The rider is scored on a similar 50-point scale, and the bull and rider scores are summed together to determine the overall competitive score for the ride. Thus, the maximum possible score for any successful ride is 100 points.
Disorders and injuries associated with bull riding have been described for human athletes of various ages and experience, ranging from professional riders4–6 to high-school athletes7 in several geographic regions. The injuries sustained by bull riders are most commonly caused by direct kicks from or trampling by the bull during a ride.8 Disorders and injuries sustained by horses during rodeo events have also been described. In a study9 of horses used for team roping competitions, heading horses (horses ridden by the rider responsible for roping the horns or head of the steer) most commonly develop lameness in the right thoracic limb, whereas heeling horses (horses ridden by the rider responsible for roping the hind feet of the steer) most commonly develop bilateral lameness of the pelvic limbs. Results of another study10 indicate that horses used for barrel racing are more likely to develop thoracic limb disorders than pelvic limb disorders. Thus, it appears that, for both human and animal rodeo athletes, the types of injuries most commonly incurred are closely associated with type of activity in which the athlete is engaged.
To our knowledge, disorders and diseases of performance-age bucking bulls have not been described. The objective of the study reported here was to characterize the medical, horn and sinus, and musculoskeletal disorders and diseases of performance-age bucking bulls. We hypothesized that the frequency of musculoskeletal and horn and sinus disorders would differ for bucking bulls, compared with that for nonbucking bulls, whereas the frequency of various diseases would be similar between bucking and nonbucking bulls.
Materials and Methods
Animals
The study had a retrospective case-control design that involved the use of a nonprobability convenience sampling technique. The electronic medical record database of the University of California-Davis Veterinary Medical Teaching Hospital was searched to identify records for bulls of Bos taurus or Bos indicus breeds ≥ 1 year old that were examined between January 1, 2000, and April 1, 2014. The age criterion (≥ 1 year) was selected because training of bucking bulls typically begins when the animals are 1 year old. Bulls were designated as cases or controls on the basis of historical information provided in the medical record or documented communication with the animal owner or trainer. Cases were defined as bulls that were designated as bucking bulls, and controls were defined as bulls that were used for nonbucking purposes. Only bulls that were examined because of a medical or musculoskeletal disorder were included in the study. Bulls that were examined for routine elective procedures (eg, health certificate, tuberculosis or brucellosis testing, age verification, hoof trim, breeding soundness examination, and cosmetic dehorning) were excluded from the study. Bulls designated as cases and for which follow-up information was unavailable or no definitive or presumptive diagnosis was recorded in the medical record were also excluded from the study. To control for breed-associated differences between cases and controls, bulls of dairy and miniature breeds were excluded from the control population.
Medical record review
For each case and control, information extracted from the medical record included examination date, signalment, history, physical examination and diagnostic test results, and clinical diagnosis. Diagnoses were classified into 1 of 3 categories (medical, horn and sinus, and musculoskeletal). All diseases were classified in the medical category. The horn and sinus and musculoskeletal categories were used to classify non-disease-related injuries or disorders on the basis of general anatomic region. Musculoskeletal disorders, including lameness, were further categorized by specific anatomic location (vertebral region, thoracic limb, pelvic limb, hoof, or other). For bulls that were examined multiple times for the same problem, only information obtained during the initial visit was evaluated. One bull (case) was examined multiple times for unrelated problems, and each problem was evaluated as a separate diagnosis.
Statistical analysis
The frequency of each disorder and disease was tabulated for both cases and controls, and descriptive statistics were generated to summarize the data. The frequency of each disorder and disease was compared between cases and controls by use of a χ2 or Fisher exact test (when individual cell counts were < 5), and the ORs and 95% CIs were calculated with controls used as the referent. All analyses were performed with commercially available statistical software,a and values of P < 0.05 were considered significant.
Results
Bulls
Seventy-eight bucking bulls (cases) and 236 nonbucking bulls (controls) were eligible for study inclusion. The mean ± SD age for the cases (5 ± 2.14 years) was significantly (P < 0.001) greater than that for the controls (3.74 ± 2.45 years), although age was not recorded in the medical record for 11 of the 78 (14%) cases and 34 of the 236 (14%) controls. Breeds represented in the case population included Brahman crossbred (n = 23 [29.5%]), mixed (15 [19.2%]), Brahman (12 [15.4%]), Brangus crossbred (7 [9%]), Angus crossbred (6 [7.7%]), Brangus (3 [3.8%]), Hereford-Brahman crossbred (2 [2.6%]), Longhorn crossbred (2 [2.6%]), unknown (2 [2.6%]), and Angus, Beefmaster, Charbray, Charolais crossbred, Santa Gertrudis, and Shorthorn (1 [1.3%] each). Breeds represented in the control population included Black Angus (n = 133 [56.4%]), unknown (16 [6.8%]), Horned Hereford (11 [4.7%]), Charolais (10 [4.2%]), Brangus (7 [3%]), Gelbvieh (7 [3%]), mixed (6 [2.5%]), Polled Hereford (6 [2.5%]), Beefmaster (4 [1.7%]), Brahman (4 [1.7%]), Limousin (3 [1.3%]), Red Angus (3 [1.3%]), Salers (3 [1.3%]), Shorthorn (3 [1.3°%]), Maine Anjou (2 [0.8°%]), Scottish Highland (2 [0.8%]), Angus crossbred (2 [0.8%]), and Belted Galloway, Brahman crossbred, Brangus crossbred, Dexter, Hereford-Brahman crossbred, Jersey-Brahman crossbred, Longhorn-Brangus crossbred, Maine Anjou crossbred, Maine Anjou-Angus crossbred, Murray Gray, Simmental, South Devon, Wagyu, and Watusi (1 [0.4%] each). One case had multiple diagnoses, and 11 controls had both a medical and musculoskeletal disorder.
Medical diagnoses
Medical disorders were identified in 15 of the 78 (19%) cases and 132 of 236 (56%) controls (Table 1). The frequency did not differ significantly between cases and controls for any medical diagnosis. Information regarding the type of restraint required for physical examination and diagnostic testing was not available for bulls with medical disorders.
Comparison of the frequency of various medical diagnoses between bucking (cases; n = 78) and nonbucking (controls; 236) beef bulls > 1 year old that were examined for a medical or musculoskeletal disorder at a veterinary teaching hospital between January 1, 2000, and April 1, 2014.
| Diagnosis | Cases (No. [%]) | Controls (No. [%]) | OR (95% CI)* | P value |
|---|---|---|---|---|
| Soft tissue abscess | 3 (3.8) | 28 (11.9) | 0.30 (0.088–1.006) | 0.051 |
| Traumatic reticuloperitonitis | 2 (2.6) | 6 (2.) | 1.01 (0.199–5.104) | 0.992 |
| Actinomycosis | 2 (2.6) | 2 (0.8) | 3.08 (0.426–22.233) | 0.265 |
| Nutritional disorder | 2 (2.6) | 2 (0.8) | 3.08 (0.426–22.233) | 0.265 |
| Paratuberculosis | 1 (1.3) | 2 (0.8) | 1.52 (0.136–16.99) | 0.734 |
| Dental disease | 1 (1.3) | 0 (0) | — | — |
| Pneumonia | 1 (1.3) | 6 (2.5) | 0.50 (0.059–4.20) | 0.522 |
| Cardiac disorder | 1 (1.3) | 3 (1.3) | 1.01 (0.103–9.84) | 0.994 |
| Indigestion | 1 (1.3) | 1 (0.4) | 3.1 (0.189–19.38) | 0.432 |
| Mites | 1 (1.3) | 1 (0.4) | 3.1 (0.189–49.38) | 0.4321 |
| Other†| 0 (0) | 81 (34.3) | — | — |
Referent was the control population.
Included genitourinary disorder (n = 53), abdominal disorder (20), squamous cell carcinoma (3), anaplasmosis (2), capture myopathy (1), bovine viral diarrhea virus infection (1), and bovine leukemia virus infection (1).
— = Not calculated.
Horn and sinus disorders
Horn and sinus disorders were identified in 10 of 78 (13%) cases and 4 of 236 (1.7%) controls (Table 2). Cases were 10.55 times (95% CI, 3.29 to 33.78; P < 0.001) as likely as controls to have horn and sinus disorders.
Comparison of frequency of various horn and sinus and musculoskeletal disorders between the cases and controls of Table 1.
| Disorder | Anatomic region | Cases (No. [%]) | Controls (No. [%]) | OR (95% CI)* | P value |
|---|---|---|---|---|---|
| Horn and sinus | Horn and sinus | 10 (12.8) | 4 (1.7) | 10.55 (3.292–33.78) | < 0.001 |
| Musculoskeletal | Vertebral region | 8 (10.3) | 2 (0.8) | 13.37 (2.78–64.42) | 0.001 |
|  | Thoracic limb | 7 (9.0) | 12 (5.1) | 1.84 (0.70–4.85) | 0.218 |
|  | Pelvic limb | 22 (28.2) | 25 (10.6) | 3.31 (1.74–6.32) | < 0.001 |
|  | Hoof | 16 (20.5) | 70 (29.7) | 0.61 (0.33–1.13) | 0.119 |
|  | Other†| 2 (2.6) | 0 (0) | — | — |
Included body wall hernia (n = 1) and preputial prolapse (1).
See Table 1 for remainder of key.
All 10 cases with a horn and sinus disorder had to be restrained in a squeeze chute for physical examination, and 8 and 3 required sedation and anesthesia, respectively, for additional diagnostic workup. Radiography was performed for 3 cases with a horn and sinus disorder. An exudate sample was collected and submitted for aerobic and anaerobic bacterial culture from 2 cases with a horn and sinus disorder. Aerobic culture yielded growth of Pasteurella multocida, Moraxella spp, Escherichia coli, Trueperella pyogenes, Aerococcus viridans, and Bacillus spp for one of those bulls and T pyogenes, Proteus vulgaris, A viridans, and Bacillus spp for the other bull. Anaerobic culture yielded growth of Fusobacterium spp, Prevotella spp, Porphyromonas levii, and Bacteroides spp for both bulls. Of the 10 cases with a horn and sinus disorder, 8 had sinusitis, 1 had a fractured horn, and 1 had an open sinus.
Musculoskeletal disorders
A musculoskeletal disorder was identified in 55 of 78 (70.5%) cases and 109 of 236 (46%) controls (Table 2). Overall, cases were 2.4 times (95% CI, 1.42 to 4.22; P = 0.001) as likely as controls to have musculoskeletal disorders. Compared with controls, cases were 13.37 times (95% CI, 2.78 to 64.42; P = 0.001) as likely to have a musculoskeletal disorder of the vertebral region and 3.31 times (95% CI, 1.74 to 6.32; P < 0.001) as likely to have a musculoskeletal disorder of a pelvic limb. The frequency of a musculoskeletal disorder of the thoracic limb and hoof did not differ significantly between cases and controls.
All 55 cases with a musculoskeletal disorder were restrained in a squeeze chute for physical examination. Of the 8 cases with a musculoskeletal disorder of the vertebral region, 4 and 1 required sedation and anesthesia, respectively, for further diagnostic workup. Additional diagnostic testing performed on the cases with a vertebral disorder included radiography (n = 6), ultrasonography (4), thermal imaging (1), myelography (1), and CSF tap and cytologic analysis of CSF fluid (3). Three cases with vertebral disorders subsequently underwent necropsy, and a vertebral fracture was identified in all 3 of those cases. Clinical diagnoses for the bulls with a musculoskeletal disorder of the vertebral region included epaxial muscle swelling (n = 1), vertebral body fracture of L1 (1), fracture of a transverse process and arthritis of the lumbosacral portion of the vertebral column (1), lumbosacral disk disease (1), presumptive rupture of the ventral vertebral ligament (1), coccygeal abscesses and osteomyelitis (1), fracture of L2 with accompanying abscesses within the spinal cord and meningitis (1), and pathological fracture and osteomyelitis of L4 (1).
Of the 7 cases with a musculoskeletal disorder of a thoracic limb, 4 required sedation for further diagnostic workup. Additional diagnostic testing performed on the cases with a thoracic limb disorder included radiography (n = 5) and ultrasonography (1). Many of those cases had multiple diagnoses. Clinical diagnoses for the cases with a thoracic limb disorder included osteomyelitis of the right humerus (n = 1); soft tissue trauma (1) and osteomyelitis (1) of the carpal joint; sequestrum within a third metacarpal bone (1); sequestra within the bones of the metacarpophalangeal (fetlock) joint (2); osteoarthritis (2), osteomyelitis (1), sepsis (1), and soft tissue swelling (1) of the fetlock joint; rupture of the lateral collateral ligament (1); and rupture of the medial collateral ligament (1).
Of the 22 cases with a musculoskeletal disorder of a pelvic limb, 12 required sedation for further diagnostic workup. Additional diagnostic testing performed on the cases with a pelvic limb disorder included radiography (n = 16), thermal imaging (1), and ultrasonography (8). Clinical diagnoses for the cases with a pelvic limb disorder included torn lateral meniscus (n = 1) and injury to a medial collateral ligament (1) of the stifle joint; slab fracture of the medial malleolus (1); avulsion fracture of the tibial crest (1); physeal fracture of the proximal portion of the tibia (1); fracture of the lateral condyle of the tibia (1); fracture of the third and fourth metatarsal bones (1); fracture of the third metatarsal bone (1); fracture of the central portion of the tarsal bone (1); fracture of the calcaneus (1); fracture of the sustentaculum tali (1); fracture of the bones of the tibiotarsal joint (1); osteoarthrosis (1), osteoarthritis (1), osteomyelitis (1), and ligament damage (2) in the tarsal joint; tenosynovitis (2) and laceration of the superficial flexor tendon (1) distal to the tarsus; and fracture of an abaxial sesamoid bone (1).
Of the 16 cases with a musculoskeletal disorder of the hoof, 9 and 1 required sedation and anesthesia, respectively, for further diagnostic workup, and 3 of those cases underwent radiography. Some of the cases had multiple hoof disorders. Clinical diagnoses for cases with hoof disorders included hoof abscess (n = 5), overgrown claw (3), coronary band laceration (2), osteoarthritis (2), hoof wall crack (2), osteomyelitis of the third phalanx (1), sepsis of a distal interphalangeal joint (1), false sole (1), sole bruise (1), presumptive fracture of the second phalanx (1), coronary band bruise (1), and hoof wall fracture (1). Of those 21 diagnoses, 18 involved a front foot and only 3 involved a hind foot.
Forty-three cases were examined because of lameness. Sixteen (37.2%) cases had a diagnosis localized to the hoof region, with only 3 (7%) localized to a hind foot. Disorders of the thoracic hoof and thoracic limb accounted for 13 (30.2%) and 19 (44.2%) of the lame cases, respectively.
Reported causes of horn and sinus and musculoskeletal disorders
For cases with horn and sinus and musculoskeletal disorders, history obtained from the owner and recorded in the medical record at the time of initial examination indicated that the disorder was presumably associated with nonspecific trauma (n = 6), pelvic limb injury after kicking a chute (5), horn or sinus infection subsequent to filing or removal of the distal portion (tipping) of the horns (4), hitting a bucking chute (4), vertebral column injury after a recent bucking event (4), thoracic limb injury following a recent bucking event (2), jumping a fence (1), fighting with another bull (1), bucking in an arena (1), bucking with a mechanical rider (1), and bucking practice on a ranch (1).
Discussion
In the present study, most of the bucking bulls evaluated had disorders of the horns and sinuses and musculoskeletal disorders, particularly of the vertebral region and pelvic limb. Bucking bulls (cases) were approximately 10.55 times as likely as nonbucking bulls (controls) to have horn and sinus disorders most likely because, compared with controls, cases are at greater risk for trauma to the head and horns and have a higher probability of having their horns tipped, which can lead to infection of the horns and sinuses. It is common for commercial beef bulls that are not used for rodeo events to be polled or dehorned. Although horns are a desirable trait for bucking bulls, bull-riding event organizers frequently require that bulls' horns be tipped.3 Tipping blunts the ends of the horns and decreases the risk for horn-induced penetrating injuries for riders and event personnel. When horns are tipped by nonveterinarians (eg, bull owners or trainers), a bull is typically restrained in a chute without sedation or anesthesia, and the distal aspect of each horn is removed with a saw. It is possible that adverse sequelae associated with horn tipping might be minimized if the procedure was required to be performed by a veterinarian. Veterinarians are knowledgeable about the anatomy of bovine horns and sinuses, local anesthesia and sedation, and indications for perioperative antimicrobial administration and have access to imaging modalities that can be used to obtain images of horns to facilitate tipping and avoid complications such as infection and sinusitis.
In commercial cattle, vertebral body fracture is associated with cattle movement and restraint and has a poor prognosis.11,12 In fact, few reports13,14 describe vertebral fracture repair in cattle. A narrow limited-contact dynamic compression plate was used to repair the fractured left transverse processes of L2 through L4 in a 3-year-old Holstein show cow with excellent functional and cosmetic results.13 In the present study, only 1 of the 78 cases had a fractured transverse process, and it is unknown whether a plating technique similar to that used in the show dairy cow13 could be used to successfully repair a transverse process fracture in a bucking bull. A narrow dynamic compression plate and plastic spinous process plates have been used to successfully repair fractures of sacral vertebrae in a dairy heifer and adult cow with excellent cosmetic results.14 It is unknown whether there is a breed predisposition for vertebral fractures. In a prospective study15 of newborn calves, vertebral fractures were identified in 6 of 86 (7.0%) calves of Danish Holstein-Friesian and Red Danish breeds but were not identified in any calves of Jersey or beef breeds. However, the investigators of that study15 attributed those fractures to trauma associated with dystocia rather than breed predisposition because manual traction was necessary to deliver all of the calves with vertebral fractures. In the present study, all 3 cases with a vertebral body fracture of a lumbar vertebra were euthanized, and the fractures were not identified until necropsy. That finding supported the results of other studies,11,12 which suggest that the prognosis is poor for cattle with vertebral body fractures of lumbar vertebrae.
The limb distribution of lameness in bucking bulls may not conform to the limb distribution of lameness in commercial cattle. Only 16 of the 43 (37%) cases evaluated for lameness in the present study had a foot disorder, and only 3 (19%) of those foot disorders involved a hind foot. Traditionally, in commercial cattle, 90% of lame cattle have foot abnormalities, and 90% of foot abnormalities involve a hind foot.16 The reason the lame bucking bulls of this study deviated from the traditional lameness patterns for cattle might be associated with the fact that those cases were examined at a referral hospital. It is likely veterinarians manage bucking bulls with routine lameness in the field rather than referring them to a tertiary hospital. It is also possible that the distribution of the weight-bearing load on the feet and legs of bucking bulls differs from that of commercial cattle. Compared with most cattle, bucking bulls must support a greater load on their front feet when their hind feet are off the ground during bucking competition and training. However, the strenuous exercise demands of bucking bulls may have a beneficial effect. Results of another study17 suggest that exercise on alternative terrain may increase the digital cushion size of dairy calves, which makes those calves less susceptible to lameness. It is possible that the digital cushions of bucking bulls are larger than those of commercial cattle, which could account for the non-traditional distribution of lameness observed for the cases of the present study.
Only 1 bucking bull of the present study had lameness that originated from a tendon injury. In a study18 of 27 cattle with traumatic flexor tendon injury, > 70% of the injuries were the result of trauma induced by farm machinery. Bucking bulls may be at less risk for that type of injury because of different management practices and exposure to farm equipment, compared with those for commercial cattle.
The frequency did not differ significantly between the cases and controls of the present study for any of the medical diagnoses evaluated (Table 1). That finding should be interpreted with caution because the number of both cases and controls with each disorder was small. It is possible that bulls with medical disorders (regardless of whether they were classified as cases or controls) are frequently managed in the field rather than referred to a teaching hospital for evaluation, whereas bulls with orthopedic disorders may require handling facilities and diagnostic modalities (eg, radiography, thermal imaging, ultrasonography) that are available only at a referral hospital.
The present study had some limitations that warrant discussion. This study was a retrospective study of cases examined at a veterinary teaching hospital over a 13.5-year period during which the approach to diagnosis and management of cases varied among attending clinicians. However, it was unlikely that the diagnostic approach used for bucking bulls changed considerably during the study period, and the effect of that limitation was considered to be of small magnitude. This was a preliminary descriptive study that involved bulls examined at a referral hospital, so the frequency of the disorders identified may not be representative of disorders of bucking bulls that are treated on-site at event venues or on the ranch by primary care veterinarians. The control population of bulls used for comparison with the bucking bulls consisted of commercial beef bulls that were not used for bull riding and were examined at the same hospital during the same time frame as the bucking bulls. Those bulls were not an ideal control population for the bucking bulls because they were not bred specifically or trained for bucking and were not managed like bucking bulls. Unfortunately, an ideal control population was not available. Finally, it is likely that physical changes to event venues such as arena flooring occurred during the study period, which could have affected our results.
Results of the present study indicated that bucking bulls were more likely than commercial (nonbucking) beef bulls to develop horn and sinus and musculoskeletal disorders, particularly of the vertebral region and thoracic limbs; however, the frequency of medical disorders did not differ significantly between bucking and nonbucking bulls. Practitioners should be cognizant of the potential safety risks associated with handling bucking bulls and the facilities and modalities (sedation and anesthesia) required to safely restrain, examine, and treat those animals. In the absence of appropriate facilities, practitioners should be prepared to refer bucking bulls to a hospital with the necessary facilities. Investigation of larger populations of bucking and nonbucking bulls than those evaluated in this study is necessary to validate the findings of the present study.
Acknowledgments
The authors thank Sophia Najera for technical assistance.
ABBREVIATIONS
| CI | Confidence interval |
Footnotes
JMP Pro, SAS Institute Inc, Cary, NC.
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