Building topline muscle and dealing with topline loss is a common struggle for horse owners.
Your horse may have a weak topline due to a variety of factors including nutrition and exercise. Physiological factors such as age or underlying health conditions can also affect topline muscle.
With the right feeding plan, exercise program, and lifestyle, you can help your horse build muscle mass and strength. Topline muscles are not only appealing to look at, but they also enhance mobility and improve overall fitness and longevity.
Topline loss often coincides with other issues that need to be properly managed. Careful examination of the horse’s daily routine and health background can help identify the underlying cause of muscle loss.
Horses with metabolic disorders such as PSSM or Cushing’s require specific approaches for supporting muscle development. Horses with gut issues and senior horses may also require special care.
We can help you develop a nutrition and management program that supports the development of healthy muscle. You can submit your horse’s diet for a free analysis by our equine nutritionists and they can give you personalized suggestions for building a better topline.
What are Topline Muscles?
The topline muscles in the horse run along the vertebral column and include the withers, back, loin and croup.
The major muscles in these areas are the Latissimus Dorsi, Longissimus Dorsi and Trapezius muscles.
In a healthy horse, the topline muscles will feel smooth and flat, and the body should appear well-rounded without excessive fat deposition.
Signs and Causes of Poor Topline
You can assess your horse’s topline condition by looking at the withers, back, loin and croup areas one at a time. If any of these areas appear sunken-in or concave, that means that there is a lack of muscle.
Overweight horses may appear to have ideal topline muscling on first observation, but subcutaneous fat may be covering the muscles.
Feeling the areas to distinguish between fat and lean tissue is helpful for accurate body condition scoring. Muscle will feel firm, whereas fat will feel spongy.
A lack of topline muscling in your horse can be attributed to many different factors, such as:
- Poor nutrition
- Old age
- Lack of movement
- Incorrect saddle fit
- Musculoskeletal issues such as polysaccharide storage myopathy (PSSM)
- Endocrine diseases such as Cushing’s disease or pituitary pars intermedia dysfunction (PPID)
If your horse is losing muscle or has struggled to attain adequate topline, these factors should be carefully evaluated by a qualified equine professional including your nutritionist or veterinarian.
How to Build Topline in your Horse
Step 1) Identify underlying conditions
Certain equine diseases like Cushing’s / PPID and PSSM can accelerate topline muscle loss. Proper diagnosis and management of these conditions with the right nutrition and exercise programs is imperative to minimize further muscle wasting.
PPID – Cushing’s Disease
The progression of Pituitary pars intermedia dysfunction (PPID) directly affects protein metabolism, which results in muscle atrophy in most affected horses.  Depending on their body condition and the presence of insulin dysregulation, horses with PPID require specialized diets catered to their individual needs.
All horses that develop PPID are at higher risk of insulin resistance and laminitis. Even if it is unclear whether your horse has IR, it is recommended to manage them as if they are insulin resistant. 
Horses with PPID that have a history of IR or laminitis require a diet very low in soluble carbohydrates, high in good quality protein and balanced vitamins and minerals. 
PSSM – Equine polysaccharide storage myopathy
PSSM, also known as EPSM, is a metabolic disorder that stems from abnormalities in carbohydrate metabolism.  Two of the most common symptoms are muscle wasting along the topline and an abnormal hindlimb gait. 
For horses diagnosed with EPSM, it is recommended to feed a diet very low in sugar and starch (less than 12% total NSC, dry matter basis), high in fat and balanced in protein, vitamins and minerals. 
Regular, consistent exercise is also strongly encouraged to control symptoms in these horses.
Step 2) Energy and protein needs
Horses that have poor topline sometimes require additional protein in their diet. For muscle growth to occur, your horse’s diet needs to provide sufficient energy and protein.
Good quality forage should be the basis of the diet and hay should be selected based on the horse’s work level and individual needs.
Depending on the energy and protein content of your horse’s forage, supplemental energy and/or protein sources may need to be added to meet your horse’s daily requirements.
Amino acids are the building blocks of protein and can be found at varying levels in different feedstuffs. There are 10 essential amino acids that must be provided in your horse’s diet because they cannot be synthesized in the body.
The total amount of dietary amino acids isn’t the only thing that matters; the proper balance of amino acids matters too. Providing a complete profile these essential amino acids will support muscle repair and recovery following exercise.
Lysine, methionine and threonine are widely considered to be the three most limiting essential amino acids in the equine diet. This means they are the most likely to be deficient in the diet. If one of these amino acids is insufficient in the diet, protein synthesis can be compromised. 
When supplementing with protein, it is important to choose good quality, highly digestible protein sources that contain these essential amino acids in the correct balance.
Some of the best high-quality protein sources to feed your horse include:
- Soybean meal
- Canola meal
- Hempseed meal
- Flaxseed meal
- Whey protein concentrate
Of these, soybean meal and canola meal have the highest lysine content and are a great choice if an amino acid deficiency is suspected.
This option may be recommended for horses that generally get enough protein in their diet but require targeted supplementation to correct for an imbalance in amino acids.