Spring has finally arrived. Your horse sheds out and to your dismay, you find that he/she has lost a topline and a tremendous amount of weight. If your horse is an older horse, you may have unique challenges to regain muscle lost.
◆︎ Why the muscle loss?
➡Muscle loss in winter is common when energy consumed is converted to heat. Discussed previously (available here), this is due to calories consumed being used to keep the horse warm.
➡In the winter, we also have the fact that hay is fed and may be marginal in amino acids necessary for building proteins, especially the limiting amino acids.
➡Couple that with the normal aging of expiring teeth and the horse may not be able to chew for as effectively to grind hay for maximum absorption.
➡Older horses may have early PPID (equine Cushing’s disease), which is very catabolic, which speeds the breakdown of muscles.
➡Additionally, older horses have waning anabolic hormones (such as testosterone and estrogen), which can help preserve muscle mass. Muscle loss due to aging has been discussed previously. Available here.
It’s easy to see why horses lose muscle.
◆︎ What can we do?
There are many steps that we can take to help horses regain muscle.
➡ Exercise: It’s important to remember that older horses will not just automatically rebuild muscle if they are sedentary, stall-bound, or with a low level of activity. This makes it difficult from a couple of aspects.
First, how can you build up to decent activity level if the horse has lost muscle mass? A structured exercise regime may be appropriate. It’s important that exercise is moderate and consistent.
Secondly, how can you devote sufficient time on a regular basis to help the horse exercise enough to build muscle? Being a weekend warrior and riding for 4 hours on the weekend will unduly tax your horse and not be consistent enough to build muscle.
➡ Feed and supplements: While it’s important to exercise, it’s also important that your horse consume sufficient calories for weight gain PLUS sufficient protein to be able to rebuild lost muscle. Supplements that may be helpful include:
▶ Equine Muscle Support is a comprehensive supplement that contains the 3 limiting amino acids, the signaling amino acid (leucine), acetyl L-carnitine for energy support for muscle development, as well as other products that support efficient muscle use.
▶ Top 4 Aminos is a blend of lysine, threonine, and methionine. Plus, it has the added amino acid, leucine. Why leucine? Leucine has been found to be a signaling molecule, which encourages muscle growth and development. Leucine is also the precursor to the expensive supplement HMB, which it touted as aiding in muscle development.
▶ Top 3 Aminos is a blend of lysine, threonine, and methionine. These were found to be limiting amino acids, with lysine being deficient in a significant number of diets.
▶ Acetyl L-Carnitine nutritionally supports the repair and development of new mitochondria within the cell. The mitochondria are the powerhouses of the cells. This is important in the muscle cell, in that it aids energy balance within the cell.
➡ Work with your vet to address underlying issues: Be sure to treat PPID where appropriate. The mere addition of supplements to support muscling may not give you the results that you hope with untreated or undertreated PPID. Without treatment, the catabolic response isn’t attenuated.
For horses with excessive muscle loss and weakness, work with your vet to develop a treatment plan. Your vet has drugs available that may be helpful, such as stanozolol (brand name Winstrol®), which is an anabolic steroid. Points to consider in support of an anabolic steroid, like stanozolol, are:
▪ It’s been used in horses previously.
▪ New research has shown that in aged mice, muscles do not have an increase in endogenous anabolic steroids to exercise like young mice do. This may be the reason why it’s more difficult to gain muscle, even when exercising the older horse. Your vet can guide you on the appropriate treatment plan.
We do the best that we can for our horses. Understanding options available to us for muscle loss is a part of that.
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Disclaimer: Statements regarding dietary supplements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease or health condition.
©Joan Kulifay 2025