These findings could eventually lead to more precise breeding for better performance, health, and welfare, and it could even help veterinarians tailor medical care, feeding, and training to individual horses. | Photo: iStock

How we feed, train, and manage horses can significantly impact their body weights. But one factor we have less control over also plays an important role: genetics.

While this isn’t a revelation in itself, what isn’t clear—or, rather, hasn’t been known until now—is which genes code for body weight. In a recent study Japanese scientists identified four genes that appear to have direct consequences on body weight in the Thoroughbred racehorses they studied.

The genes—LCORL, ZFAT, TRIB2, and MSTN—are found, respectively, on Chromosomes 3, 9, 15, and 18. Combined, these genes accounted for 17% of the body weight differences in more than 800 3-year-olds. When factored in with sex differences, they accounted for a full 30%