Influence of different exercise regimes on the proximal hoof circumference in young Thoroughbred horses

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.

To investigate the effect of training on proximal hoof circumference in young Thoroughbred racehorses being prepared for racing.

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.

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.

Horses showed a decrease in circumference during race training that reversed when they were rested.

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.