Relationships Between Measurements of Body Fat in Thoroughbred Horses

Equine obesity is increasing in prevalence, and weight loss diets are frequently recommended for these horses. However, there are also management situations in which horses are deemed to be too thin. To monitor the efficacy of weight change programs, estimates of body fat are often made. There are several systems available to estimate body fat, and there are benefits and challenges to using each method. The objective of this study was to compare four different methods of estimating body fat in Thoroughbred horses. In 14 mature Thoroughbred horses, relationships among body condition score (BCS), morphometric measurements, ultrasonic measures of subcutaneous fat depots, and estimation of total body fat (BF_D) via measurement of total body water through deuterium oxide dilution were evaluated. Body condition scores ranged from 4.5 to 6.5 on a 9-point scale. Body condition score, heart girth-to-body weight ratio, and BF_D were all positively correlated with each other (P < .05). Subcutaneous fat depth at the tailhead tended to be positively related to BF_D when only horses with BCS ≥ 5 were included (P = .0680). These data suggest that BCS remains a simple means of monitoring adiposity in mature horses in moderate condition. Tailhead fat depots may become useful for monitoring changes in body fat in Thoroughbreds with a BCS above 5, although more work with animals of higher adiposity is required and at different times of year.