Chapter 107The European Thoroughbred
As long as people have ridden horses, matches of speed have been held informally between proud owner-riders. Racing horses under saddle was certainly established in England by the time of the Roman occupation. Chester boasts the longest running unbroken series of race meetings in the United Kingdom on the original site, the strangely named Roodeye. This area of land (translated, island of the cross) has been used for horse racing continuously since 1539. Interestingly, racing was introduced to replace football (soccer), which had been banned a few years earlier because of the number of severe injuries and fatalities it produced. The original prize money was substantial for the time, being “in the XXXI yere (31st year) of King Henry Theght (VIII), a bell of sylver, to the value of three shillings and three pence, is ordayned to be the reward of that horse which shall runne before all others.”
Since the time of James I (1603 to 1625), a link has existed between royalty and the town of Newmarket in Suffolk, leading to its reputation as the headquarters of racing in the United Kingdom. Charles I, the successor of James I, established regular spring and autumn race meetings in Newmarket and built a palace and stables, some of which have survived. Racing at that time consisted of matches between pairs of horses, over long distances by modern standards, usually accompanied by hefty personal wagers between their aristocratic owners. Distances as long as 4 to 6 miles were not unusual. During the succeeding two centuries the race distances declined, as did the age at which horses were allowed to race. Initially horses had to be older than 5 years of age, but this was reduced gradually until in 1859 even yearlings were allowed to race. This practice soon ceased, but 2-year-old racing had become established and became, unfortunately in the opinions of many, part of the Thoroughbred (TB) spectrum. During this time the breed itself changed considerably.
Arab horses had been imported sporadically to Britain from the time of the Crusades (twelfth century AD). Usually seized in battle, these Arab horses would have been relatively slow and sturdy horses, used for carrying warriors into battle. In the seventeenth century, a marriage alliance between Charles I and the Portuguese Royal Household allowed Charles access to the Arab horses of the Barbary Coast, and several stallions made the long journey, mainly over land, back to the United Kingdom. Three horses alone—the Byerley Turk, the Darley Arabian, and the Godolphin Barb—founded the entire breed of the TB we know today, producing profound changes in size and conformation from the native English stock. Eighty percent of the TB racehorses alive today are descended from just one of these stallions, the Darley Arabian, through his great-great-grandson Eclipse.
As the distance of races decreased, speed became an increasing factor, and the fields of competitors increased in size. Eventually the handicap system was introduced in an attempt to avoid the dominance of the sport by a few exceptionally gifted individual horses. All this led to an increase in interest in racing as a spectator sport and a vehicle for gambling. From the nineteenth century onward, racing was more or less recognizable as the sport we enjoy today.
The most prestigious races in Europe belong to a worldwide system of accreditation, which groups together races of similar standing. The best horses competing at top level meet each other in a group of internationally acknowledged races known as Group 1. This group includes all the classics in the United Kingdom and the most prestigious races throughout Europe and North America. Beneath Group 1 are two other groupings (Group 2 and Group 3) for horses that have excellent ability but are not up to the extreme rigors of Group 1 racing. Competitors in these races face a weight for performance penalty system. For example, a Group 1 winner running in a Group 2 race carries a weight penalty in an attempt to equalize the competition.
The next tier down from Group races includes the Listed races. Again, the International Pattern Committee decides which races are of sufficient stature to belong to this list. Usually horses enter a Listed race when they have already won a maiden and possibly another race with specific conditions. Such horses have few other realistic options because after two wins a horse carries a lot of weight in an open handicap. Often success in a Listed race increases potential breeding value far more than winning such a handicap. These limited opportunities are often the reason why horses that are good, but not good enough to be top class, are sold out of Europe to continue racing in North America, where races are more suitable. Horses racing in North America are also often able to recoup in prize money the owner’s investment, a situation that is often impossible racing in Europe, with its relatively lower prize money.
Beneath the upper echelon of horses racing in Listed and Group company is an open handicap system in which horses are allocated weight according to speed rating. These speed ratings are assessed by professional handicappers, who monitor the performance of the horses when they run in the first three maiden races or less if they win. The horse’s rating rises and falls during its racing career, depending on its most recent form. Although this system is obviously open to abuse by trainers running horses at inappropriate distances or on unsuitable ground to lower their racing weight, the system does allow horses of moderate or differing ability to compete against one another on near equal footing and produce an exciting finish. The handicappers’ dream is of all horses finishing within a length or so of each other.
Until recently all flat racing in the United Kingdom took place on turf. This led to a certain divergence in bloodlines and ability patterns of racehorses in North America and Europe. About 20 years ago, all-weather racing on a synthetic surface was developed at two tracks, Lingfield and Southwell. Although initially introduced for hurdle racing as a way of keeping the betting public satisfied when the National Hunt cards had to be abandoned through bad weather, both tracks rapidly discontinued hurdle racing on all-weather surfaces because of the high injury rate. This left the way open for flat racing on the all-weather tracks to become established. Since that time, new synthetic tracks have also opened at Wolverhampton, Kempton, and Great Leighs.
The synthetic all-weather track surface is not the same as the dirt commonly used in North America. The depth of the cushion is greater, and the material is a composite of oil, plastics, fibers, and sand. Few races with large prize money are run on the synthetic surfaces, and the racing has tended to be of a more humble grade, but that is slowly beginning to change. These tracks give horses of limited ability somewhere to race and also allow trainers with small stables to compete with each other in the absence of both top-level horses and the larger yards, although this too is beginning to change. Several successful all-weather horses have made a transition to racing in North America to end up running in Group (graded stakes) races on dirt, and the all-weather surface can act to some extent as a screening academy to pick out horses that seem particularly adept at performing on these artificial surfaces, although not all horses make a successful transition from synthetic surfaces to dirt racing.
Flat racing is popular in the United Kingdom, Ireland, and France but less so in the rest of Europe. Although training centers exist in Germany along with a substantial number of high-grade races, flat racing has not really caught the imagination of the public in the same way as in Britain and Ireland and receives little media attention. Ireland always has had a strong tradition of horsemanship, and racing, centered around the Curragh, is buoyant and popular. Standardbred racing is equally popular in France, Germany, and Scandinavia, where flat racing opportunities are limited. Many European countries enjoy racing in the absence of a substantial breeding industry, and this creates a market for the surplus racehorses produced and raced in the United Kingdom, Ireland, and France. Horses in these countries are raced at 2 years of age and, ability permitting, 3 years of age, and at the end of the 3-year-old career many are submitted for sale if they have not shown sufficient ability to be retained for racing as older horses. This makes room in the yards for the incoming yearlings. These large dispersal sales at the end of the 3-year-old career supply the horses for National Hunt racing in the United Kingdom and for flat racing areas of the world lacking breeding programs. The need for yards to clear out the less gifted 3-year-olds to make room for the influx of yearlings also produces enormous pressure on trainers and consequently their veterinary surgeons to have a racehorse fit and able to race at 2 and 3 years of age, often without consideration for the long-term consequences of any treatments.
The small window of opportunity available to these horses impinges directly on many of the surgical and medical management decisions that need to be made when problems arise. The economics and practicality of any advice given have to be considered from the owner’s viewpoint and the welfare of the horse.
One of the major differences between training and racing in North America and Europe is in the geographical location and logistics of stabling and training of the horses. In the United States, almost all horses train at the racetrack and are stabled there continuously. In Europe, the horses live and train in yards often well away from the racetrack. These yards tend to be clustered around a training area, with gallops and conditioning canters available for use by local trainers. The horses travel daily to race at racecourses that may be up to 200 miles away.
In the United States, the horses, trainers, jockeys, and veterinary surgeons tend to move from one racecourse to another, but they stay at each track for long periods. Racing at each location takes place for many days or even weeks before horses and trainers move on to another track. Although some horses stay behind at one track, racing does not occur at that track when the primary focus is elsewhere.
In Europe, racing seldom occurs at any one racecourse for more than 3 consecutive days. Horses are trained in traditional stables, some of which date back many centuries. Horses travel to racecourses the day before racing, if the journey is particularly long, or even on the day of the race. Some horses make extremely long round trips. For example, it is not unusual for a trainer in Arundel on the south coast to send horses as far north as Ayr in Scotland, a round trip of 936 miles. Obviously the cost of transport has to be weighed against the potential gains, but the traditional system of training and traveling to the races in the United Kingdom seems to be holding up for now.
In 2000, two of the all-weather racetracks opened training barns adjacent to the track with a view to introducing American-style training, track side. How popular and successful this system is going to be and whether it will spread to other racecourses remain to be seen.
In North America, almost all training and racing takes place on a left circle (counterclockwise), and this might be expected to have influences on the incidence rates of injury to the left and right limbs for many lesions, such as proximal sesamoid bone (PSB) fractures, third metacarpal (McIII)/metatarsal (MtIII) bone condylar fractures, and tendonitis (see Chapter 106). In the United Kingdom, much conditioning work and even race speed training take place in straight lines (Figure 107-1). Racing itself can be on straight tracks (e.g., 1000 and 2000 Guineas at Newmarket), predominantly to the left (Epsom Derby), or to the right (Doncaster St. Ledger). The tracks themselves divide into about one third right-handed and two thirds left-handed throughout the country. This has an important impact on the lack of specific incidence of injury to the left or right limbs. One large fracture survey in Newmarket showed few instances of left or right dominance for any injury.1
Fig. 107-1 A, Horses approach the finish of the long and lonely Rowley mile racetrack at Newmarket. This photograph illustrates the undulating nature of the straight 1-mile track over which both 3-year-old Group 1 classics are run. B, The long straight of the training track gallops up Warren Hill just outside Newmarket. Two different all-weather synthetic surfaces are also available (between the white railings). The rest of the heath is used in strips, which are changed daily using movable markers. Each strip of grass is used only once every 3 years.
Yearlings arrive in the yards for breaking from the sales in September and October and, unlike the situation in North America, often go straight to the trainer for breaking rather than to a specialist pretraining center.
After breaking, the yearlings usually start steady cantering exercise until Christmas. As the racing season approaches, horses showing precocity and ability to withstand faster exercise step up in pace throughout February and March. The first 2-year-old races occur in April, encouraging hard training of skeletally immature horses. However, until the racing calendar changes and while these races are open and available, trainers will train horses for them.
All-weather racing has altered the seasonal impact of flat racing in the United Kingdom forever, and some flat race horses now train throughout the year. However, most of the high-quality flat race horses do not compete on the all-weather circuit and are put into a slow-speed maintenance program from November until January, involving light cantering and trotting. Fillies may be turned out for a period.
All this is substantially different from the position in North America, where the horses often do not arrive at the racetrack until they are fully broken, in cantering exercise, and ready to do fast work. The breaking and pretraining often takes place in specialized pretraining centers, away from the city center tracks. This has important effects on the perception of racetrack veterinarians in North America concerning the incidence of developmental orthopedic disease linked to lameness. In North America, developmental orthopedic disease often causes lameness leading to diagnosis and removal from training before a horse reaches the racetrack; therefore horses with developmental orthopedic disease are not commonly seen by track veterinarians. An example is a subchondral bone cyst in the medial femoral condyle. Subchondral bone cysts are a regular occurrence in the annual intake of yearlings in the United Kingdom, diagnosed by the trainers’ veterinarians. Discussion with colleagues working at California racetracks reveals that they rarely see horses with subchondral bone cysts, presumably because of the effect of the earlier screening at the pretraining centers.
Once on the track in North America the racing is often less seasonal and less age specific, removing a lot of the pressure for success at 2 or 3 years of age within a short season. Whether a horse races on turf or dirt does not matter: historically, all training took place on dirt, and this should be borne in mind by veterinarians assessing horses for potential purchase to move from Europe to America. Asking potential purchasers whether the horse is intended for turf or dirt racing is largely irrelevant because the daily training almost certainly will be on dirt. The dirt surface is more testing in many ways than anything these horses have seen before, and horses able to train and perform well on grass sometimes fail to make the transition to dirt. In the past couple years, a few training tracks and racetracks in North America have moved to synthetic surfaces. It will be interesting to see whether this makes for an easier transition for horses moving from Europe to race in North America, and what impact it has on the types and frequency of training and racing injuries.
Taking a detailed history is a prerequisite for a medical examination in any species. In racehorse practice one often sees a succession of lame horses during any morning in several different yards, and the detailed information may be limited. The trainer may not be present to supply it. However, one should always try to ascertain the following information before examining a TB racehorse for lameness:
Stress-induced bone injuries are more likely to become apparent as work intensity increases. Stress-induced bone injuries include all of the long bone stress fractures of the humerus, tibia, the McIII, and the MtIII, and the ilial wing and shaft of the pelvis. Similarly, in a 2-year-old that has reached advanced training speed, the carpus and metacarpophalangeal joint are common sources of forelimb lameness, and lateral condylar stress injuries of the MtIII are common causes of hindlimb lameness. A 2-year-old in advanced training is less likely to have lameness associated with a subchondral bone cyst, osseous cystlike lesion, or OCD because these lesions usually cause lameness when the horse is younger and beginning its conditioning exercise. However, occasionally subchondral bone cysts and osseous cystlike lesions may arise or result in clinical signs for the first time at 3 years of age or even older.
In horses with acute-onset, severe lameness, questions of clinical history become less important because the horse is often not bearing weight, and a suspicion of skeletal failure is raised. Knowing whether this horse has been a good mover before onset of severe lameness is often helpful because some injuries (McIII/MtIII bone condylar fractures, PSB fractures) often are associated with poor gait before the actual fracture takes place. The same is true of horses with slab fractures of the third carpal bone, which often are preceded by a long period of subchondral bone sclerosis associated with bilateral third carpal bone pain (Figure 107-2). One of the most useful questions to ask about a horse with severe lameness is what stage of training the horse has reached because only advanced training to fast canter or gallop speeds usually results in bone failure. However, bacterial infection subcutaneously or within the hoof also can produce severe lameness.
Fig. 107-2 Flexed dorsal 60° proximal-dorsodistal oblique radiographic images of the left third carpal bone (C3) of three Thoroughbreds (TBs). Lateral is to the right. A, Normal. However, this complete lack of increased radiopacity is rare in a TB in advanced training, most of which show some degree of radiopacity of the radial fossa of C3. B, Dense increased radiopacity of the radial fossa of C3. Normal trabecular pattern is lost, and the bone has a “ground glass” appearance. There is increased osteolysis at the site of a normal nutrient foramen (arrow in the center of increased radiopacity). This stiffening of the bone predisposes it to injury or fracture. C, A nondisplaced sagittal fracture of C3 that propagates through the center of an area of severe increased radiopacity representing mineralization of bone (arrows).
The veterinarian always should get the horse out and see it walk and trot to determine which limb is lame. Riders are notoriously unreliable at detecting the correct lame limb. The veterinarian should determine whether the lameness is unilateral or bilateral by the way the horse moves. Many racehorses are slightly lame in all limbs and have a typical crouching, shuffling trot or may try repeatedly to break into a canter because trotting is so uncomfortable. New lameness may be superimposed on a chronic level of unsoundness.
Increasing experience usually leads one away from the belief that any one injury is linked to a particular gait. Lameness typical of a shoulder or a stifle tends to become a more remote belief because so-called typical lamenesses so often are linked eventually to the most unexpected site. However, a few types of lameness do remain that seem to be linked to one particular pathological syndrome. Young TBs often show bilateral forelimb lameness related to carpal pain. These horses often trot with the limbs abducted from the midline and not fully flexed during forward motion. This gives a rolling, stiff-legged forelimb gait. The horse’s attempt to get the contralateral limb down quickly to get off the sore limb as soon as possible shortens the forward phase of the stride, leading to a choppy, stilted action. However, horses affected with bilateral front fetlock pain or PSD trot in a very similar way if the pain level is the same in both limbs, and it may simply be that because carpal lameness is a common manifestation of this gait, we have come to link the two more firmly than we should.
Pain associated with the metatarsophalangeal joint is often bilateral and leads to a fairly characteristic gait typified by low limb flight, often with dragging of the toe during protraction, and an exaggerated rocking pelvic excursion dorsoventrally on both sides (sometimes termed the Marilyn Monroe trot) because the horse dips off each painful limb. Horses with a humeral stress fracture often abduct the limb, with shortened cranial protraction at the walk. One Newmarket trainer described this gait recently as “trotting like a pig in a tight skirt,” which, although not a likely scenario, is in fact just how they look..
Having ascertained which limb is the lamest, the limb should be examined in detail using basic examination protocols (see Chapters 4 through 8 and 10). The following specific points apply to the TB racehorse.
Running a finger distally on the shin with a horse bearing weight often causes a horse to buckle the limb even if it has been months or even years after shin soreness has subsided and is not a reliable diagnostic test.
Fig. 107-3 Application of torsion to the tibia. The metatarsophalangeal joint is rotated medially, the os calcis laterally, and firm shoulder pressure maintained with the stifle. Horses with a stress fracture of the tibia often show a sharp pain response to this test and will often be unwilling to bear weight on the limb for some seconds subsequently.
Many lesions in the TB racehorse are associated with subtle changes in bone density and structure rather than overt fragmentation of bone. These variations result in subtle changes in radiopacity (increased radiolucency or radiopacity), which often are seen best on high-quality radiographs using single-screen film and excellent radiographic technique or more recently by using digital radiography. However, we should be aware when using digital radiography that the “standard” appearance of bone is lost. By altering the algorithms and scaling, we can alter contrast and obliterate the signs of increased radiopacity of bone at will. This is particularly true in appraisal of the “skyline” projection of the third carpal bone, where assessment of increased radiopacity is critical in advising on future workload of young horses and can be made MORE difficult by the ease of image manipulation now available to us digitally.
Radiography is notoriously unreliable in detecting early fracture lines and subchondral bone collapse. For this reason, if lameness is linked to a particular site by diagnostic analgesia and nothing is visible radiologically, repeating the radiography 2 weeks later is often advisable. Any horse with subtle changes in bone density can be rested long enough where additional damage can be seen. During investigation of individual joints, special projections are often most useful (Figure 107-4). Radiographic examination of the metacarpophalangeal and metatarsophalangeal joints always should include the flexed dorsopalmar image, which is extremely useful for evaluating the palmar and plantar aspect of the condyles (see Figures 107-4 and 107-5).3,4 In a hindlimb this view often is achieved best as a plantarodorsal image. The limb is cupped loosely by a hand underneath the tarsus and allowed to hang in a semiflexed position. The cassette is placed in a cassette holder and positioned on the dorsal aspect of the metatarsophalangeal joint, and the x-ray machine is positioned above and behind to achieve the orthodox 125-degrees image.
Fig. 107-4 A, Weight-bearing dorsal 20° proximal-palmarodistal oblique radiographic image of a right metacarpophalangeal (MCP) joint. Lateral is to the left. No gross abnormality is seen. B, Flexed dorsal 125° distal-palmaroproximal oblique radiographic image of the same MCP joint. There is an incomplete linear fracture (arrow) in the lateral condyle that was not visible on any other image.
Fig. 107-5 A, Dorsal 60° proximal-palmarodistal oblique image of the left metacarpophalangeal (MCP) joint; lateral is to the right. This steeply angled dorsopalmar image was developed in an attempt to see subchondral bone change diagnosed by magnetic resonance imaging examination, but not seen on conventional radiographs. There is a zone of severe bone mineralization (increased radiopacity, arrows) associated with an advanced subchondral bone injury in the medial condyle. Normal trabecular pattern of the condyle is lost (cf., lateral condyle). B, Dorsal 60° proximal-palmarodistal oblique image of a right fore MCP joint; lateral is to the left. There is less marked mineralization of the medial condyle (white arrows) than in A, but there is radiolucency/fissuring in the most palmar portion of the parasagittal aspect of the medial condyle (black arrows). This horse was lame at the walk, and pain was localized to the MCP joint by local analgesia. This fissuring was not visible on orthodox radiographic images. C, Dorsal 30° proximal 45° lateral-plantarodistal medial oblique image. This image highlights the region of the lateral condyle in contact with the lateral proximal sesamoid bone when the joint is at full weight bearing, a common site of focal stress injury. Focal bone mineralization (increased radiopacity) is evident (white arrows) with a central area of radiolucency (black arrow), which probably represents bone necrosis and resorption. This degree of change is usually irreversible and associated with chronic lameness. These changes cannot be seen on any other radiographic image.
The lateral condyle of the MtIII bone is a predilection site for subchondral bone injury, represented by sclerosis in the early stages and subchondral bone loss and radiolucency as the condition advances. This can be highlighted by a dorsal 30° proximal 45° lateral–plantarodistal medial oblique image (down angled oblique) developed by Ross5 (see Figure 107-5, C).