Risk factors for being an unsuccessful two-year-old race horse
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Abstract Background The primary reason for the loss of horses from training and racing is musculoskeletal injury, especially dorsal metacarpal disease. Research has shown that the occurrence of injuries is related to the intensity of the exercise programme. Short periods of high speed exercise in the training seem to be beneficial, as especially bones can adapt to the high speed, so horses are better prepared for racing speeds. Aims To describe the differences between horses who go straight through training as a two-year-old and horse who have interruptions in their training. Methods The data, containing 597 two-year-horses, were obtained by Perkins over a 34-months period from October 1997 until July 2000. For every horse the training activity score (TAS) was recorded, as well as the amount of days it had spent in that TAS. Different TAS were: TAS 1= spell, TAS 2= walk/trot, TAS 3= canter, TAS 4= gallop/high speed exercise, TAS 5= starting in a race or trial. Also recorded were the reasons why horses were put on a spell; voluntary or injury related. Results The two-year-olds were divided in three different groups: “Good” horses (n=279, no spells), “Voluntary” horses (n=144, just voluntary spells) and “Involuntary” horses (n=132, at least one injury-related spell). There was a significant difference between the good group and the voluntary/involuntary group in TAS already at the start. The voluntary and involuntary groups both had a big dip in TAS at the beginning of training, but after that the voluntary group went significantly faster to reach TAS 5 than the involuntary group (p<0.05). Of the voluntary group 50% of the horses reached TAS 5. Of the involuntary horses only 30% reached TAS 5. Of all the horses that reached TAS 5, the good horses (median=114 days) were significantly faster (p<0.01) to reach TAS 5 than the voluntary/involuntary horses. There was no difference between the voluntary (median=244 days) and involuntary groups (median=244 days). Voluntary horses were faster to reach their first spell than involuntary horses (p<0.01). Both groups had their first spell early in the training. Involuntary horses had more than one spell more often than voluntary horses. In the good group, older two-year-olds were faster to reach TAS 5 than the youngest (p<0.01) and middle (p=0.028) groups of two-year-olds. In the voluntary group, the middle group of two-year olds were faster to reach TAS 5 than the early two-year-olds (p=0.014). Horses that were born in the year 1995 were faster to reach TAS 5 than horses born in the year 1996 (p=0.013) and the year 1997 (p=0.003). Conclusions The critical point of horses ending up in a group is early on in the training. Trainers may have a good view on whether a horse is going to be a good one and they will train such a horse quickly up to TAS 5. Voluntary horses might be the horses that are obviously not ready to cope with the training and are put on a spell by their trainer. Involuntary horses could be the horses that the trainers were in doubt about whether to put them on a spell or not, then were trained further and subsequently sustained an injury. When in doubt it would therefore be wise to put the horse on a voluntary spell, as horses in this group have a much higher chance of reaching TAS 5 and a lower chance of being put on another spell, than horses in the involuntary group. Late two-year-olds have an advantage on younger two-year-olds. This could be due to these horses being stronger and more developed or having received more pre-training. There is an effect in the year of birth the horses were born in. This shows that factors such as weather and track conditions have their influence.