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.

Many breeding stallions that come from the racetrack have poor hoof quality, underrun heels, long toes, and thin soles, predisposing them to sore feet. The feet should be observed daily and trimmed every 4 to 6 weeks. Leaving stallions barefoot is best, but some may require front shoes to remain comfortable. Rarely, bilateral hind foot pain can cause similar clinical signs, and hind shoes with corrective trimming may be necessary (Editors). These horses may be left barefoot during the off season to allow the feet to grow more normally. Provision of soft footing in the breeding shed and weight control are important. Pain control using NSAIDs may be necessary.

Fractures of the Distal Phalanx

Fractures of the distal phalanx can be acute or chronic injuries. Most are palmar process fractures, and horses can be managed with a bar shoe with side clips reset every 6 weeks, stall rest, and NSAIDs. Sagittal fractures of the distal phalanx are more serious, but horses may be managed in the same way.

Laminitis

Common primary causes of laminitis include contralateral orthopedic injuries, colitis, Potomac horse fever, Salmonella, and other infectious diseases that predispose to the release of endotoxins. The treatment of horses with acute laminitis includes treating the primary disease, supporting the distal phalanx, decreasing blood pressure, treating inflammation, and managing pain (see Chapter 34).^14-16

Chronic laminitis, with rotation of the distal phalanx, can be an important problem in breeding stallions, manifested as a stiff gait or more overt lameness in one or both front feet. Trimming, shoeing, and providing analgesia are important (see Chapter 34).

Muscle Disease

Rhabdomyolysis and other muscle diseases are usually evident during or after thrusting. Inefficient thrusting on early mounts is followed by increasing discomfort, leading to rapid mounting and dismounting. The horse may sweat profusely and have an increased respiratory rate and obvious pain. Treatment during an acute episode includes administering acepromazine (10 to 20 mg intravenously) to control anxiety and 10 to 20 L of balanced electrolyte solution intravenously, keeping the horse confined to a stall, monitoring progress, and evaluating the stallion closely for paraphimosis. In horses with chronic rhabdomyolysis, the diet should be altered to primarily hay and high-quality, low-protein, low-carbohydrate feed.¹⁷ Methocarbamol (see Table 127-1) is useful in some horses.

Injuries

Injuries in stallions, including lacerations, punctures, abrasions, and fractures or dislocations, are managed similarly as in other horses. A common injury is abrasion or contusion of the carpus during mounting, especially with dummy mounts. A stallion with a painful carpus may fail to grasp a mare with the forelimb and may stand up on the mare or dummy. Sexual rest until the wound heals is usually best. If continued breeding is necessary, emollient topical analgesic ointment and skillful bandaging from the coronet to several centimeters above the carpus can relieve apparent discomfort, with the administration of NSAIDs if required.

Hyperextension injuries of a forelimb may occur at dismount but are usually not serious and resolve with NSAID treatment.

Aortoiliac Thrombosis

Signs suggesting aortoiliac disease include delayed ejaculation despite good libido (numerous mounts and more than 12 thrusts); progressive hindlimb weakness or pain during thrusting resulting in camping under the mare or dummy; and difficulty backing up to dismount.¹⁸ Erection aberrations are not as common as ejaculatory dysfunction, but they can include delayed or rapid tumescence or detumescence, or loss of erection during thrusting.

Pain Management

Phenylbutazone is the most common NSAID used for breeding stallions. A 4-week oral treatment course (2.2 mg/kg twice daily) has no adverse effects on semen quality at the time of ejaculation or after 24 and 48 hours stored at 4° C.⁸ Although fertility trials have not been done, clinical experience suggests no adverse effects of chronic treatment with phenylbutazone at levels tolerated well by a stallion. We recommend orally administered phenylbutazone daily throughout the breeding season to keep the stallion comfortable and functioning with as little effort and pain as possible to avoid a potential downward spiral of delayed ejaculation, additional effort, and exacerbated lameness.

Firocoxib is now available for horses. Although not specifically tested in breeding stallions, efficacy for lameness has been reported to be similar to that of phenylbutazone.¹⁹

We have used gabapentin clinically in combination with phenylbutazone in an attempt to help breeding stallions with possible neurogenic and musculoskeletal discomfort.²⁰ Early studies indicate that oral bioavailability of gabapentin is low compared with intravenous administration but is well tolerated at 20 mg/kg.²¹

Complementary pain management, including acupuncture,^5,6 electrostimulation, and massage therapy, may provide additional comfort, with no adverse effects, on semen quality or fertility.

Fitness and Weight Management

Routine exercise is one of the most important management factors for maintaining cardiovascular and musculoskeletal physical and mental fitness of any breeding stallion. A general recommendation for exercise for a sound breeding stallion is daily paddock exercise for a minimum of 8 hours or a minimum of 30 minutes of supervised exercise or light work. Although the common tendency is to rest a lame horse, controlled exercise is probably even more important for breeding efficiency of a lame stallion. A daily exercise program, including turnout or supervised light work, appears to clinically significantly improve the breeding efficiency of a lame stallion. The type of exercise is influenced by the degree of lameness and the temperament of the stallion. Controlled exercise may include daily riding, lunging, jogging, swimming, or exercise on a treadmill or mechanical walker.

Libido and breeding efficiency almost always improve with a stallion carrying less rather than more body weight, particularly for hindlimb lameness or incoordination. We have seen remarkable improvement in breeding efficiency and stamina after reduction in body weight in Quarter Horses with small sore feet or in stallions with aortoiliac thrombosis.

Breeding Management and Handling

Breeding Shed Handling Considerations

Most disabled stallions benefit from having the mare or dummy mount slightly down grade. This can reduce the work of the hindlimbs in supporting the body weight. For a live mount mare, a down grade is achieved best with a sloping ramp extending at least 3 m behind, in front, and to each side of the mare (Figure 127-1). A height differential between the stallion and the mare can be built with mats or by placing the mare in a pit. These work well if the mare remains stationary, but if the mare moves back, the grade may be reversed for the stallion. If the mare moves forward, the stallion can become trapped between the mare and the front edge of mats, or in the pit with the mare. When breeding a stallion with the mare downhill, it is important to avoid the peak of a knoll that slopes off to the sides, behind the stallion, or in front of the stallion. This sets the stallion up to fall sideways should the mare move sideways or to be at further disadvantage if the mare moves backward. Once the stallion mounts, restraint of the mare should be optimized to reduce movement in any direction. Disabled stallions that are tentative to mount also can be deterred by low ceilings, cornered mares, or dummy mounts.

Fig. 127-1 Mare positioned down grade for breeding.

When using a dummy mount for stallions with hindlimb, back, or neck problems, we find that greater heights are better. Most disabled stallions do better when guided to remain mounted squarely from the rear, as opposed to across the dummy, or traveling up the side. This is best accomplished by securing the artificial vagina at a physiological angle against the dummy for the stallion to serve, rather than taking the artificial vagina to the horse.

Excellent footing in the breeding area, which is customized to a stallion’s particular needs, can improve breeding efficiency greatly (Table 127-2). The surface should be nonslip even when wet, seamless and even to avoid stumbling, and provide moderate cushion. Stallions with hindlimb weakness or incoordination tend to camp under the mare. For these stallions the footing behind the mare is critical to maximize the ability to correct the stance. Although some cushion is good, it should not be so spongy or deep that the stallion gets caught up or buried in the substrate. Stallions with sore feet, especially front feet, benefit from a softer footing, particularly a soft landing during dismount. Heavy sod on well-drained soil is often the simplest and best outdoor footing. Composite rubber athletic surfaces, particularly if poured and seamless, make ideal breeding surfaces.

TABLE 127-2 Flooring Materials for Breeding Sheds*

A stallion should be given ample freedom about the head, particularly during mounting and thrusting, to allow postural adjustments. Enforcing routines that work well for sound stallions, such as always keeping the head on the left side of the mare or dummy mount, may discourage a disabled horse. For severely ataxic, weak, or uncomfortable stallions, thrusting and ejaculation can be facilitated with gentle stabilizing assistance or spotting during breeding. We recommend an assistant apply gentle pressure with the hands on one or both hips to support the stallion from falling (Figure 127-2). Some stallions tolerate support from the rear, for example, with a wide strap held from either side behind the buttocks. Some resent this type of support, appearing to become trapped on the mare.

Fig. 127-2 Spotting a stallion on the left side during breeding.

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Gentle, guiding handling during dismount is important for all stallions but particularly for a disabled horse. For stallions with hindlimb weakness, pain, or incoordination, special consideration should be given to allowing the stallion as much recovery time as possible before dismount and to moving the mare slowly out from under the stallion rather than forcing the stallion to back off. Ataxic stallions that tend to step on themselves and the mare while breeding can benefit from simple, well-secured protective boots or wraps for themselves and the mare.

Sore Feet

It is recommended that maiden mares should arrive on a breeding farm at least 8 to 10 weeks before the beginning of the breeding season. This allows time to assess and monitor condition of the feet and time for trimming as needed. Early arrival also affords time to acclimate the horse to the farm routine and social environment and for advanced photoperiod manipulation (under lights). Simple sore feet are a common problem in a maiden mare coming from the racetrack. The mare may have thin-walled feet and soles, underrun heels, long toes, bruised feet, quarter cracks, or corns. The mare may have been shod for a long time and not be accustomed to being barefoot. If sore feet are suspected as a cause of lameness, the feet should be examined with hoof testers. Baseline radiography may be indicated. Soaking, poulticing, sole painting, and the administration of phenylbutazone or flunixin meglumine (see Table 127-1) may be required for effective management of mares with foot soreness. Feet of broodmares should be trimmed every 6 to 8 weeks and ideally mares should be barefoot on all limbs and certainly for the hindlimbs.

A subsolar abscess is the most common cause of acute foot pain (see Chapter 28). Other causes include a sequestrum, laminitis, or a fracture of a palmar process of the distal phalanx. A sequestrum of the distal phalanx may be removed in a standing horse,²⁸ eliminating the risks of general anesthesia for a developing fetus.

Laminitis

Acute or chronic laminitis can be a management problem in mares and may be secondary to pleuritis, diarrhea, severe lameness, or most commonly after foaling followed by a retained placenta (more common in draft breeds; see Chapter 125) or infectious metritis. Chronic laminitis also occurs in overweight mares, mares with a previous history of laminitis, or those that have ingested large amounts of feed or fresh pasture. Acute or chronic laminitis can have a negative effect on fertility secondary to pain.²⁷

The treatment goals in broodmares with acute laminitis and chronic laminitis are similar to those described for the stallion. In our experience, some mares with chronic laminitis can be salvaged as successful broodmares with careful foot care, pain medication, good footing, separation from other broodmares and associated competition, and management similar to that described for the breeding stallion. In addition, some can conceive and deliver a normal foal, if these management techniques are successful. However, reproductive lives are often limited by laminitis.

Osteoarthritis

A broodmare with OA may need confinement to a stall or small paddock and analgesic medication (see Table 127-1). With severe OA of the fetlock or carpus, arthrodesis may be considered as a last resort in a broodmare that can no longer conceive or maintain a foal because of chronic pain.

Enlarged or Swollen Limbs

Palmar or plantar dermatitis of the pastern (scratches or mud fever) secondary to wet or muddy footing may cause lameness, particularly in hindlimbs. The mare should be removed from the wet area. Local therapy may be necessary, including washing, drying, and clipping the affected area and local application of a steroid/triple antibiotic topical ointment.

Lymphangitis is seen most commonly in the hindlimbs, is worse in later pregnancy, and causes reluctance to move, painful and pitting edema, and fever. Treatment includes stall rest, antibiotic therapy, and phenylbutazone.

A puncture wound and secondary cellulitis may cause lameness. Locating the original wound is often difficult. Aggressive antibiotic and antiinflammatory therapy is necessary. Additional treatment may include surgical drainage, hot packs, warm water hosing, and bandaging.

Hindlimb lameness may be associated with mastitis. The udder is painful to touch; the mare may not allow the foal to nurse; her appetite may decrease; and she may be febrile. Lameness resolves with symptomatic treatment of the mastitis.

Rhabdomyolysis

Acute rhabdomyolysis occurs occasionally in late gestation after particularly vigorous exercise. The mare may not come in for normal feeding or night stables and is often anxious, has a stiff walk, and may have dark-colored urine. Diagnosis is confirmed by measurement of serum creatine kinase levels. Treatment includes stall rest and NSAIDs. A mare with a foal at foot can be treated with the foal present.

Foaling-Related Injuries

Obturator nerve paralysis secondary to dystocia can result in mild to severe lameness. The mare may show difficulty in abducting the hindlimb and standing immediately after foaling. Femoral nerve paralysis secondary to dystocia results in inability to fix the patella and therefore the hindlimb. This is seen immediately after foaling. Symptomatic therapy for either condition includes NSAIDs, supportive therapy, nursing care, such as slinging if necessary, and adequate bedding and footing. The prognosis for full recovery is guarded, and a nurse mare may be needed for the foal.

Prepubic tendon rupture or ventral body wall hernias may occur during late gestation, apparently without reason. Ventral edema cranial to the udder is severe, unilaterally or bilaterally. An affected mare may have difficulty rising. It is difficult to obtain an accurate diagnosis until edema resolves after foaling. The body wall enlarges in the ventral flank. Diagnostic tests include palpation per rectum and ultrasonography. Occasionally, a tear in the ventral body wall can be palpated per rectum. Supportive treatment consists of NSAIDs, physical support of the enlarged area using large bandages, restricted exercise, close monitoring before and during foaling, a laxative diet, and assisted early induction of foaling. Successful surgical repair of ruptured prepubic tendons and large ventral body wall hernias is often unrewarding, but smaller defects can be repaired successfully. The prognosis for mares with large tears of a ruptured prepubic tendon and future use as broodmares is guarded to poor.²⁹ Embryo transfer may be a reasonable alternative in breeds that allow this form of management (the Editors).

Neurological Disease

The most common neurological disease of adult broodmares in the United States is EPM. Cervical vertebral malformation also occurs and should be distinguished because treatment is different. Treatment for EPM is as for a stallion, but folate supplementation is not recommended in broodmares receiving pyrimethamine because of the potential alteration in organogenesis.³⁰

Old Injuries

Many broodmares have old superficial digital flexor tendon or suspensory ligament injuries that may deteriorate, or mares may sustain acute reinjury. Aged broodmares may have gradual thickening and lengthening of the hindlimb suspensory ligaments. Broodmares with acute reinjuries are treated by restricted exercise, analgesia if needed, local therapy, and ultrasonographic monitoring. Stall confinement with daily handwalking may be needed for 3 to 4 months, depending on ultrasonographic evidence of healing. Treatment of mares with hindlimb suspensory desmitis with a dropped fetlock consists of strict stall confinement, pain medication if needed, and application of an extended heel, egg bar shoe. This shoe should be removed just before foaling for safety.

Occasionally, older broodmares develop extensive new bone, especially around the carpus, causing lameness. The mare should be separated from the normal herd to reduce competition for food and water, with restricted exercise and analgesia provided.