Muscle mass scoring system for horses developed

Researchers have developed a new five-point scale to identify differences in muscle mass between horses, relying on visual appearance and palpation.

University of Copenhagen researchers Kristine Pallesen, Katia Gebara, Charlotte Hopster-Iversen and Lise Berg described their development of the equine muscle condition score (MCS) in the journal Equine Veterinary Education.

The study team said muscle mass affects both performance and health in horses. It is therefore important to be able to easily evaluate their muscle mass.

The researchers set out to create a system able to be used by veterinarians, owners, trainers and others involved in horse management and training.

Their work centered on 25 Thoroughbreds at different training levels. Initial assessments of all horses included their body condition score, height and bodyweight.

The study team then imaged seven muscles using ultrasonography and measured them. They were the musculus splenius, m. brachiocephalicus, m. multifidus, m. longissimus dorsi, m. gluteus medius, m. semitendinosus and m. tensor fascia latae.

The muscles were selected based on their ability to be measured using ultrasound, their biomechanical function, and a desire to avoid areas where fat is typically deposited in horses with higher body condition scores.

Beforehand, the researchers tested ultrasonographic measurements by assessing each muscle 10 times in two horses. Variation tended to be under 5%.

Muscle sizes were compared between the trained and untrained Thoroughbreds to determine muscle mass differences, and the animals were ranked according to measured muscle mass.

This led to the development of a five-point scale, with the researchers relating the ultrasonography results to what could be seen and felt through palpation.

Palpable and visual differences between horses at different ranks were identified, they said.

The muscle condition score was subsequently tested by an independent, blinded operator in all 25 horses.

The study team reported that all muscle sizes were significantly correlated to each other except for m. brachiocephalicus, which was not correlated to m. semitendinosus and m. multifidus.

“All muscles were significantly larger in trained horses than in untrained horses except for m. brachiocephalicus and m. splenius,” they said.

After testing, minor adjustments were made to optimise usability of the score.

Their system, they said, should enable veterinarians, trainers and horse owners to make quick and reliable overall assessments of muscle mass in horses.

The authors acknowledged that the study population comprised very similar horses. “Further studies are needed to test the reliability of the muscle condition score in horses of different breeds, disciplines, body condition scores and health.”

Pallesen, K., Gebara, K., Hopster-Iversen, C. & Berg, L.C. (2023) Development of an equine muscle condition score. Equine Veterinary Education, 35, e 550–e 562. Available from: https://doi.org/10.1111/eve.13777

The study, published under a Creative Commons License, can be read here.