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Study: Majority of Horses Considered ‘Lefties’

Wither measurements of 490 horses taken with a flexible tracing tool have shown that the majority of horses have larger measurements on the left side of their withers as compared to their right, suggesting they are “lefties.” Dr. Katrina Merkies, with the University of Guelph, and a team of undergraduate students digitized and compared years of measurement data to come to this conclusion.

The study included a variety of breeds, including finer-boned breeds like Thoroughbreds and Arabians to heavier breeds like Warmbloods and draft horses. Overall, 60 percent of study horses had larger muscles on the left sides of their withers.

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Merkies and her team considered laterality as a possibility for why horses have a tendency to build muscle on the left. Laterality refers to a horse's preference for using one side of his body. The right side of the brain controls the left side of the body and this is where fearful stimuli are processed, the team reported. Merkies noted that horses will often look at an object they are afraid of out of their left eye or step off trailers with their left front leg first, both of which reinforce the notion that these horses are “lefties.”

While examining differences in body sizes and shapes, the scientists also found that horses of medium height were more likely to have more-curved backs than their brethren of other sizes. The team hypothesize that this is because medium-sized horses are often ridden by adults, whose saddle might not properly fit, being too long in the seat and applying pressure to the lumbar region.

Pressure from an ill-fitting saddle can cause pain and affect performance, as well as prevent the muscles from building in a symmetrical way. Merkies stated that proper and twice-yearly saddle fittings are imperative for equine comfort and the development of balanced muscles.

Sore Back? Skip The Bute

Horse owners have been known to take medications prescribed to the animals in their care, despite the possible dangers. While some anti-inflammatories, antibiotics, and dewormers may be the same in both human and equine medicine, but their formulations can be vastly different; because of this, human ingestion of equine drugs isn't recommended.

An American woman experiencing severe back pain attempted to take some phenylbutazone (Bute) that had been prescribed for one of the horses in her care. She took three doses of the non-steroidal anti-inflammatory drug (NSAID), each suitable for a 400-pound horse, reports the journal Clinics and Practice.

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Three days later, the woman went to the hospital complaining of nausea, vomiting and weakness, which she said she had been experiencing for two weeks. She often had back pain that was controlled by use of over-the-counter naproxen, but reported that this episode was exceptionally painful, which is why she ingested the Bute.

She presented to the hospital with nearly low blood pressure, a high heart rate, and normal O2 levels, as well as dry mucous membranes. Blood work showed a low white blood count, low platelet levels, elevated liver enzymes, and acute kidney injury. Her urine blood screen showed use of amphetamines and marijuana.

Poison control and toxicology were engaged once it was discovered she had ingested the Bute, but no antidote was recommended. She was given an N-acetyl cysteine and sodium bicarbonate drip because of the suspected acute liver damage caused by the phenylbutazone.

After three days of in-hospital treatment, the woman was feeling better and checked herself out.

Though phenylbutazone was used in human medicine for the treatment of multiple forms of arthritis, it was removed from the human medicinal arsenal in 1970 because of an increased risk of agranulocytosis, a life-threatening blood disorder.