Weigh tape more accurately estimates equine body weight than morphometric formula: a controlled technical assessment

Accurate body weight (BW) estimation in horses is essential for clinical and nutritional management; however, calibrated scales are often unavailable under field conditions.

To compare the longitudinal accuracy and consistency of a commercial weigh tape and the Carroll and Huntington morphometric formula against calibrated digital scale measurements in adult horses.

In a prospective longitudinal experimental study, six clinically healthy adult crossbred horses (mean real body weight [Rbw] 355.5 ± 21.2 kg) were monitored weekly for 63 days under controlled management conditions. BW was measured using a calibrated digital scale (Rbw), a commercial weigh tape (Tape), and the Carroll and Huntington formula (Formula). Agreement, estimation error, and variability between methods were evaluated using mixed-effects regression models and correlation analyses.

Mean Rbw increased from 355.5 ± 21.2 kg at baseline to 372.7 ± 27.0 kg at day 63 (+17.2 kg; +4.83%). Both indirect methods overestimated BW throughout the study period; however, Tape estimates showed lower mean overestimation (+2.48%) than Formula estimates (+9.89%). The minimum estimation error for Tape decreased from 8.33 kg at baseline to 5.66 kg at day 63, whereas Formula errors remained consistently higher (37.2-45.6 kg). Correlation with scale measurements was stronger for Tape (r = 0.916) than for Formula (r = 0.821). Mixed-effects models demonstrated lower variability and improved temporal consistency for Tape estimates.

Both indirect methods remained within clinically acceptable estimation limits; however, the commercial weigh tape provided greater accuracy, lower variability, and better longitudinal consistency than the morphometric formula under controlled conditions.