Factors Affecting Weigh Tape Reading in the Measurement of Equine Body Weight

SIMPLE SUMMARY: Different methods can be used for measuring a horse’s body weight, including a specific equine weigh tape, which gives a body weight estimate based on the heart girth circumference. Since more accurate equine weighbridges are not easily available due to high cost, weigh tapes are a common method of estimating body weight in horses. However, this measurement is not always accurate, with different factors potentially affecting tape readings. Therefore, the aim of this study was to investigate which variables affect weigh tape readings. Using a large data set, available through a commercial horse feed company, the results suggested that weigh tape readings may be influenced by breed, bone density, and body fat coverage. These results will help give a greater understanding and aid in the interpretation of weigh tape measurements in the future. ABSTRACT: Accurate measurement of equine body weight is important for evaluating medication dosages and feed quantities. Different methods exist for measuring body weight, including weigh tapes (WT), though accuracy varies. Measurements could be affected by external variables, such as time of day, human error, or uneven surfaces, and also horse-based variables, such as height and body condition score (BCS). The aim of this study was to investigate how different horse-based variables affect WT reading. A retrospective analysis was performed using anonymised data from feed company nutrition consultations (Baileys Horse Feeds). Data included a range of horse-based variables, a WT reading, and true body weight measured on a weighbridge. All horses were over two years of age. Likelihood ratio tests were used to assess whether adding different horse-based variables significantly improved the fit of the quadratic regression model. The variables included were height, BCS, breed, muscle top-line score, and bone type. Exploratory analysis showed that the WT generally underestimated body weight, particularly for horses with higher body weight. Adding height and muscle top-line scores did not significantly improve the fit of the model, suggesting no influence on WT reading over and above actual body weight. Adding breed groupings, BCS, and bone density did improve the fit. Each 0.5 unit increase in BCS increased the WT estimate by 1.24 kg (p < 0.001). These results confirm that a WT does not provide accurate body weight measurements, and generally underestimates body weight, though more so for heavier horses, being more accurate in pony breeds.