Reasons for performing study: Most lameness in horses relates to foot problems and may be associated with changes in hoof shape, but there is a lack of information on the influence of normal exercise on hoof shape.
Objectives: To investigate the effect of training on proximal hoof circumference in young Thoroughbred racehorses being prepared for racing.
Methods: Thirty-seven young Thoroughbred racehorses were included in this study. Front hoof circumference immediately below the coronary band was measured weekly with a measuring tape in all horses present at the stable. Most horses accomplished a minimum of 2 training periods at the stable separated by periods of rest on a paddock. One sample t tests were used to evaluate if the mean change per week differed from zero. To estimate the repeatability coefficient, the left proximal hoof circumference of 25 horses was measured 3 times in a random order on one day.
Results: Most horses showed a similar pattern of change. The proximal hoof circumference decreased during the training periods (P<0.0001) and increased when the horse was rested (P<0.0001). The decrease of the circumference during the first training period was -0.66 mm/week on the left and -0.64 mm/week on the right. During the second training period, this was -0.58 mm/week on the left and -0.57 mm/week on the right. During the rest period, the circumference increased by 1.03 mm/week on the left and 1.12 mm/week on the right. The repeatability coefficient for the left circumference was 1.8 mm.
Conclusions: Horses showed a decrease in circumference during race training that reversed when they were rested.
Potential relevance: Measurement of front hoof circumference is a simple method to assess change in hoof shape. It provides an opportunity to investigate the relationships between specific training, hoof shape and soundness.
