TDK conference 2016

The accurate measurement of weight is required for administration of anthelmintics, anaesthetics and other drugs to avoid under- or overdosing. As scales are rarely accessible for horse owners and ambulatory equine veterinarians, determination of drug doses is based on body weight estimation. Because of the inaccuracy of visual body weight estimation, several formulas have been made during the last 50 years to define the bodyweight of horses by measuring the length of their body parts. These models are recommended for adult horses or foals older than 6 months. The aim of our study was to investigate the usability of these previous models on foals and also to establish a new weight estimation method which is suitable for foals under the age of 6 months. Ninety-eight healthy, warmblood foals (43 colts and 55 fillies) with normal body condition were included in the study. The examined population consisted of 71 Sport Horses, 12 Arabians and 14 Standardbreds aged between 1 and 186 days. The foals were divided into groups by their breed, sex and age. On each of them, the following variables were measured: height at the withers, hip height, heart girth, umbilical girth, length of the body, neck circumference, circumference and length of the tarsus, circumference and length of the carpus. After these measurements, the foals were weighed on a calibrated digital scale. Linear regression analysis was done and then the variables were substituted in the previously published formulas for adult horses. The formulas were compared with Bland-Altman plots.Out of the previous methods, the Carol-Huntington formula (bodyweight=heart girth2xbody length/11877) estimated the real bodyweight most accurately (mean of differences: 6.47, Sdiff: 9.037, standard error of measurement: 6.39). Depending on the bodyweight of the foals we modified the denominator of the Carol-Huntington formula from 11877 to 11364 (mean of differences: -0.45, Sdiff: 9.36, standard error of measurement: 6.63). The formula created by us is based on the volume of a truncated cone in contrast to the Carol-Huntington formula which is based on the volume of a cylinder. (mean of differences: -1.035, Sdiff: 9.77, standard error of measurement: 6.91) In conclusion, out of the formulas the most accurate and practical is the Carol-Huntington, because it defines the bodyweight of foals in the most accurate way with fewer variables.