Measuring the height of ponies at the withers: Influence of time of day, water and feed withdrawal, weight-carrying, exercise and sedation

Measuring the height at the withers of a pony is one of the requirements of the Fédération Equestre Internationale (FEI), before competitors can participate in an official pony event. A pony has to be measured each year until it is eight years old. With and without shoes the height at the withers must be below 149.0 cm and 148.0 cm, respectively. When a pony exceeds the regulated height, it is excluded from participating in FEI pony competitions. Besides being excluded from competing, the selling price of the pony decreases dramatically, because the animal is then classified as a horse. For these reasons some owners may be tempted to try to influence wither height. The aim of the study was to determine whether the height of a pony at the withers can be influenced by variables such as time of day, water and feed withdrawal, weight carrying, exercise or sedation. To see if there was any influence of these variables on the measured height, the animals were measured at the beginning of the experiment and after completion, according to a standardized protocol.Fifteen healthy horses aged 7–17 years old and 16 healthy ponies aged 5–18 years were used for the study. A statistical evaluation determined whether there was a significant difference between the height at the withers before and after the experiment (P < 0.05). Time of day, water and feed withdrawal, carrying weight, exercise and sedation all tended to decrease the height at the withers, but, with the exception of the data collected from the sedation-trial, the results were not significant. At the beginning of the experiment, the mean height at the withers of all eight animals was 165.0 ± 4.6 cm; 15 min after giving a standard dose of 5 μg/kg detomidine-HCl per horse IV, the mean height had decreased to 163.7 ± 4.5 cm. Even 2 h after administration of the sedative, the mean height at the withers was still 163.7 ± 4.6 cm. However, at both measuring points, it was still clinically apparent that the animals were sedated. The results demonstrate that it is not possible for owners to significantly influence the height at the withers except by administrating a sedative.