Fat or Flat? Understanding Body Condition vs Muscle Mass in Horses
As winter comes to an end, it’s time to look beneath the rug—literally—and understand the difference between fat stores and muscle tone in your horse’s body. Because what you see isn’t always what you get.
Body Condition vs Muscle Score: Why It Matters
As we reach the tail end of winter, it’s common to see the toll the season has taken on our horses. Winter rugs can hide a multitude of sins, and with declining pasture quality and hay not always being up to its usual standard, some horses may have lost condition without us realising it.
On top of that, many horses are given a break from regular work during winter—turned out for rest, not competing or exercising as often. Just like us, when the workload drops off, so can muscle tone.
But here’s the question: if you see a horse in the paddock that looks thin, is it due to poor body condition—or is it muscle loss? And what about the horse that looks overweight—are you seeing fat deposits or well-developed muscle from consistent training?
These two assessments—body condition score and muscle score—are often confused. It's not uncommon to hear reports of horses being underweight when, in fact, they’re lacking muscle, not fat. So, how do you tell the difference?
What is Body Condition Score?
Body condition—or body score—is a measure of the amount of fat a horse carries. This assessment is based on visual inspection and palpation of key areas: the neck, withers, ribs, loin, and tailhead.
It’s also important to factor in life stage and circumstances. For example, has the horse just been relocated, recovered from illness, foaled recently, or is currently in foal? These all influence fat storage.
The most widely recognised system is the Henneke Body Condition Score, developed in 1983 by Dr. Don Henneke for Quarter Horse broodmares. It uses a scale from 1 (emaciated) to 9 (obese) and is now industry standard.
Before assuming mistreatment based on body score alone, it’s essential to consider contributing factors
Low Score High Score
Age-related changes Diet too rich for workload
Dental issues Insufficient exercise
Illness or metabolic disorders Genetic predisposition to obesity
Laminitis or Cushing’s (PPID) Overfeeding or food dominance in herd
Parasites or poor grazing Poor feeding management
Emotional stress or herd dynamics
Lactation demands
What is Muscle Score?
Muscle scoring evaluates muscle mass, focusing on atrophy (loss) or hypertrophy (increase). Unlike fat, muscle is directly influenced by exercise, injury, breed type, and nutritional intake—particularly protein.
It’s critical to assess muscle in context. A Clydesdale will naturally have larger pectorals and hindquarter muscles due to their draft work, whereas a Thoroughbred typically shows lean muscle with minimal fat due to their speed-based design.
In 2022, Kentucky Equine Research developed the MASS (Muscle Atrophy Scoring System), which evaluates muscle in four regions: neck, back, abdomen, and hindquarters. Horses with PPID (Cushing’s disease) were excluded from their study due to known impacts on muscle mass.
Key Causes of Muscle Loss (Atrophy):
Aging
Illness or PPID
Poor protein intake
Injuries or nerve damage
Ill-fitting tack
Lack of correct exercise
Key Causes of Muscle Gain (Hypertrophy):
Genetics (e.g. Quarter Horses)
High protein intake
Correct and consistent workload
Discipline-specific training
One of the most misunderstood areas is the topline—a sunken look along the back often gets mistaken for swayback or assumed skeletal issues. In reality, it may simply indicate weak core muscles that need strengthening.
Another area often misjudged is around the sacrum and tailhead, where sloping or sunken musculature can mimic signs of kissing spine. But remember, only diagnostic imaging (like X-rays) can confirm a kissing spine diagnosis—never visual observation alone.
Body condition and muscle mass are two distinct yet intertwined elements of equine health. Both influence how your horse looks and performs, and both can be improved with the right combination of nutrition, exercise, and bodywork.
As the seasons shift, now is the perfect time to reassess what’s under the rug. Is it fat? Is it muscle? Or is it something more? Knowing the difference helps you make better decisions for your horse’s health and performance—and deepens the partnership you share.
Written by Linda Bolton-Breen - Breton Equine Wellness
