Bovine Reproduction. Группа авторов
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Rupture of the Gastrocnemius
In commercial cattle, rupture of the gastrocnemius tendon is induced by aggressive mounting behavior by an oversized herd sire or slipping in an already unhealthy individual. It can also be seen in cows undergoing reproductive procedures. If an epidural goes too high, the motor control to the hindlimbs can be affected. As the cow comes out of the chute, she can get her legs caught in a brisket bar or slip on concrete. The injury most often occurs at the junction of muscle and tendon and is quite obvious in the standing animal. The hock is markedly flexed and may even drop to the ground; the fetlock is simultaneously flexed. The diagnosis can be confirmed with ultrasonography. The condition is usually unilateral, but if the patient continues to struggle the contralateral tendon can also be damaged. Complete rupture of one or both tendons has a grave prognosis. Partial rupture of one or both tendons has a better prognosis but is rarely observed in cattle since most occur in fractious patients and quickly proceeds to complete rupture. Treatment involves a full limb cast or Thomas/Walker splint. Healing usually involves six weeks of immobilization and four weeks of stall confinement. NSAIDs should be used during recovery (Figure 16.23).
Figure 16.23 Bilateral partial rupture of the gastrocmenius tendon from its associated muscle.
Osteochondrosis Dissecans
Osteochondrosis dissecans (OCD) is a common cause of lameness in cattle, particularly those being fitted for show, fed for sale, or being pushed for performance. It is often management induced in cattle with a genetic predisposition, particularly in club calves. Factors leading to OCD development include:
Excessive feeding with subsequent excessive weight gain
Lack of proper mineral supplementation leading to mineral imbalance, complicated by increased mineral requirements due to breed variances
Feeding of distillate products with high sulfur content
Lack of opportunity for skeletal maturity.
The most common location for OCD in the hindlimb is in the tarsus and the medial malleolus of the tibia; it develops less commonly on the lateral femoral condyle, the tibial plateau, and the medial and lateral trochlear ridges of the talus. In the forelimb, the primary site is the medial surface of the humeral condyle, though osteochondrosis can appear in any joint [17, 18] (Figures 16.24 and 16.25).
Figure 16.24 Osteochrondrosis lesion in a yearling bull from gain test. Notice the medical malleolar fragment (upper circle) and the cyst in the medial condyle of the talus.
Figure 16.25 Typical appearance of an OCD‐affected tarsus (boggy hock).
Surgical management of OCD and OCD fragments is preferred to slow down or stop the progression of inflammation and subsequent degeneration occurring within the affected joint. When anatomically possible, the OCD lesion should be debrided by curettage and overdrilling or implantation of a compression screw above the lesion (Figure 16.26).
Figure 16.26 Osteochrondrosis lesion in the talus of a show steer.
Medical management of cattle with OCD fragments is generally palliative in nature and often does not resolve the lameness, particularly in the growing animal. NSAIDs, stall rest, and intra‐articular injection of long‐acting anti‐inflammatories are utilized. However, as cattle get heavier and more weight is placed on the affected joint, clinical lameness may become worse.
Bone Fractures
Fractures in the bovine often occur due to inappropriate management, such as mishandling, crowding, or improper handling facilities. The duty of the practitioner is to evaluate the fracture and determine whether economical repair or salvage is most appropriate. Fractures of the rear limbs often occur due to trauma from other cattle; the tibia is the most commonly affected of the long bones when this occurs.
Physical examination and palpation with manual manipulation of the limb can be helpful to assess the extent of the injury. Radiographs are necessary to determine if the fracture is comminuted or involves a joint that may not be readily apparent on physical examination. Attention should also be given to soft tissue injuries that may have damaged the vascular supply. Damage to the dermis may result in sloughing tissue and exposure of the fracture. Crushing injuries of the digital vasculature and metacarpus can happen after forced fetal extraction during dystocia. Consideration should be given to sepsis at the fracture site, particularly in older fractures, as hematogenous spread of bacteria in the bovine can occur.
Cattle with fractures of the distal limb, forelimb, or hindlimb heal extremely well. Even comminuted and compound fractures can resolve if proper immobilization and therapy are provided. The most common method of repair in simple fractures is passive fixation with a cast. A half‐limb cast is used for fractures below the carpus or tarsus.
Comminuted or compound fractures of the digits usually require a more rigid immobilization in order to get adequate healing in a reasonable amount of time. Of great value in complete immobilization is the traction/pin cast, which involves incorporation of wires passing through holes drilled in the rear abaxial walls of the hoof. This also serves to allow the assistant to properly position/align the limb for casting. Transfixation or transcortical pins are usually placed at some point in the lower to mid‐third of metacarpal (MCIIII) or metatarsal III (MTIII) to provide for weight transfer to the cast. Predrilling of a slightly smaller hole (0.5 m or less than the pin diameter) will reduce thermal injury to the bone during pin placement. Oftentimes, only one pin is needed to properly provide for weight transfer in younger animals. Threaded transcortical pin systems are preferred in older, heavier cattle, usually requiring placement of two pins at least 1.5 inches