Do owners administer inappropriate doses of anthelmintic based on an inaccurate perception of their horse's bodyweight?

Abstract

Background: Inaccurate dosing and repeated administration of anthelmintic from the same drug class are indicated as factors associated with equine helminth resistance; and resistance is specifically related to the under-dosing of anthelmintic products. Research indicates that many owners may still rely on visual estimation to determine a horse's bodyweight. Aim: The pilot study aimed to investigate whether owners administer inappropriate doses of anthelmintic based on an inaccurate perception of their horse's bodyweight. Method: Data were collected from 16 horse owners with varying experience and from a variety of equine disciplines. A series of questions were presented in order to capture specific information. Owners were asked to provide the dose of anthelmintic (kg) that they had most recently administered to their horse, to estimate the bodyweight of their horse, and to provide a body condition score (BCS) for their horse using the guide provided. Each horse was then weighed on an equine weighbridge to obtain an accurate bodyweight. The estimated bodyweight was compared with that of the accurate bodyweight, and the most recently administered dose of anthelmintic was compared with both the estimated bodyweight and the accurate bodyweight. The BCS provided by each owner was compared with that of the BCS provided by the researcher. Data were tested for normal distribution using a Shapiro-Wilks test, and analysed using an independent-samples t-test or a paired-samples t-test. Results: All of the owners inaccurately estimated the bodyweight of their horse, however there was no statistically significant difference between the estimated bodyweight and the accurate bodyweight (p=0.738). Owners with less experience more accurately estimated the bodyweight of their horse when compared with owners with more experience, but there was no statistically significant difference in accuracy between the two groups (p=0.085). There was no statistically significant difference between the accurate bodyweight and the dose of anthelmintic that owners had administered to their horse (p=0.074), but there was a statistically significant difference between the estimated bodyweight and the dose of anthelmintic that owners had administered to their horse (p=0.034). Conclusion: Horse owners administer inappropriate doses of equine anthelmintic based on an inaccurate perception of their horse's bodyweight, however the horse's estimated bodyweight does not appear to be the only influencing factor when deciding on the dose of anthelmintic to be administered.