Sore Back

A sore back is associated with inadequate coupling and thrusting during breeding. A stallion may fail to wrap the pelvis or neck around the mare or dummy and may tend to hold its head off the neck of the mare and paddle with the forelimbs. Thrusting is often of irregular depth and rhythm, that is, choppy and interrupted. An acutely sore back may become a chronic condition, exacerbated by breeding and an increased number of unsuccessful mounts, unless treated aggressively.

It is important to determine the primary cause of lameness and initiate the appropriate treatment. Pain can be secondary to another musculoskeletal cause such as OA, a heavy breeding schedule, poor footing, poor shoeing, poor fitting of the breeding dummy to the stallion, or allowing the stallion to advance up the side of a dummy mount so that it is thrusting with a curved back. Chronic back pain may be treated using acupuncture once weekly for 8 weeks and repeated every 3 to 4 weeks or as needed.⁵ Acupuncture therapy may be combined with nonsteroidal antiinflammatory drug (NSAID) therapy, or NSAIDs may be used alone.^5,6

Prognosis for normal breeding performance is guarded to good and varies with management factors. One key factor is ejaculatory efficiency. Once a stallion needs more than one or two mounts per breeding, expected performance diminishes rapidly.

Osteoarthritis

A stallion with OA appears stiff and painful during breeding; stiffness is often worse after rest and improves with exercise. The carpus, front fetlocks, and hocks are affected most commonly. Diagnosis may be obvious on physical examination and is confirmed radiologically.

Pain control is essential to maintain adequate breeding performance. We recommend phenylbutazone (1.5 to 2 g orally [PO] twice daily for 4 to 5 days and then 1 g twice daily for 5 to 7 days)⁷ combined with a period of sexual and general rest if possible. Clinically significant improvement may not be evident for up to 5 to 10 days. Long-term, low-dose phenylbutazone treatment has no measurable effect on sperm production or testicular size,⁸ but horses should be monitored for signs of toxicity, including colic, loss of appetite, diarrhea, dependent edema, and mucosal ulceration or renal disease.⁹ Other NSAIDs, such as flunixin meglumine and ketoprofen, and intraarticular or systemic medication with corticosteroids, polysulfated glycosaminoglycans, and hyaluronan may be useful in selected horses.

Arthrodesis may be warranted for severe OA of the fetlock joint, but postoperative pain may persist, requiring long-term management. Pancarpal arthrodesis may be considered for stallions with severe carpal OA or after acute, severe carpal injury. With any lameness, pain management must be used to prevent increased recumbency, which can compromise thermal regulation of the testes, especially in hot conditions, and reduce sperm viability and fertility.

Neurological Disease

Neurological disease (see also Chapter 11) is usually evident during mounting, intromission, and thrusting, with a stallion stepping on its hind feet, bearing weight on a toe rather than the sole, and sometimes knuckling over. The stallion may bear weight unevenly during thrusting, sometimes becoming high sided on the mare or dummy mount, or falling. The stallion may have reduced proprioceptive control of the penis in seeking and intromission and may have poor anal tone during thrusting. The horse may require extraordinary effort to ejaculate.

Treatment of cervical vertebral malformation (CVM) in adult horses is challenging, and management methods are important, including good footing, proper shoeing, proper positioning of the mare or dummy mount, ground collection of semen, and pharmacological aids to ejaculation when necessary (Box 127-1).^1,10 Special precautions must be taken during collection of semen or breeding to protect the stallion, the mare, and the personnel working around the stallion. The mare or dummy mount should be positioned to minimize the risk of a stallion with poor lateral stability falling. Lateral support can be provided at the hips. For semen collection, a mare that does not wiggle from side to side should be used. A dummy mount may be better but usually elicits less vigorous thrusting than a live mount and cannot be moved forward to assist the stallion with dismounting. Surgery occasionally is performed, with recovery taking many months.¹¹

The management of horses with EPM (see Chapter 11) is similar to that for horses with CVM, together with daily pyrimethamine and sulfadiazine or sulfamethoxazole for at least 60 to 90 days (Table 127-1). To prevent anemia, supplementation with folate and vitamin E is advised.¹² This treatment does not affect sperm production adversely.¹³

TABLE 127-1 Medications

Sore Feet

Signs of sore hind feet include shallow thrusting, failure to plant the feet securely during thrusting, thrusting on one leg, and early dismount. Signs of sore front feet or other forelimb pain include hesitancy to mount and dismount. If not resolved quickly, sore feet can lead to long-lasting psychogenic sexual behavior dysfunction.

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