Review: The importance of overall body fat content in horses

In several livestock species, body condition can positively affect reproductive function. In horses, predictions of body fat (BF, %) are useful in achieving maximum reproductive efficiency, cost-effective nutritional management, and management of obesity-related health conditions. For decades, BF in horses has been predicted by an equation using ultrasonic scans of rump fat thickness, but the most commonly used practice by producers to evaluate energy status is the BCS system. However, the BCS system is subjective and exposed to variation, sometimes to a great extent, among evaluators. Recently, deuterium oxide (D₂O) dilution has been validated as an accurate, objective, and minimally invasive method to estimate BF in ponies. Similarly, strong correlations have been observed between D₂O estimations of BF and BF determined by near-infrared spectroscopic analysis. Reported in only a few studies, the relationship between BCS and BF is inconclusive. In moderate to obese ponies, BCS was not found to be a sensitive indicator of BF. Conversely, data from 24 stock-type horses in our study indicated that BCS might be useful in estimating BF. In addition, research suggests that physical measurements and peripheral leptin concentrations may be used to assess energy status in horses. More investigation in these areas is warranted because there is currently limited lipid research in the equine industry.