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Among horse owners, a persistent rumor circulates suggesting that it is possible to enhance a horse’s muscle development through protein-rich dietary supplementation. It is indisputable that protein plays a crucial role in muscle development. Muscle development in horses, akin to humans, is contingent upon their level of physical activity.

In the absence of proper training, a horse will not attain the muscular development typically associated with sport horses.

Nevertheless, horses – especially when fed a “nutritious” diet with a high proportion of concentrated feed – often look very well muscled, even though they are not really working at all. There are two reasons for this: First, there are genetic factors that naturally influence how muscular a horse appears. So, a cold-blooded horse will tend to appear more muscular and have a fuller hindquarters compared to a thoroughbred.

But having a solid muscle foundation doesn’t necessarily indicate strength, endurance, or performance. Particularly with thoroughbreds or endurance horses, it’s common to wonder where they find the strength for their performance, given that they often appear slender but tough..

Another factor that contributes to muscle growth is, in fact, their diet. When a horse is provided with an excess of energy, especially from sources like sugar, starch, fat, and protein found in concentrated feed or rich pasture grass, many horse breeds tend to convert this surplus energy into fat.

Unlike humans, though, this fat doesn’t accumulate as soft padding on the hips. Instead, horses store fat as ‘strands’ within their muscles. This results in the muscles appearing more voluminous and trained, even though it doesn’t actually represent an increase in muscle mass.

To ensure effective performance from working muscles, two key factors come into play: proper training and the composition of protein. Three amino acids are crucial for muscle building, as the body cannot produce them on its own: Lysine, methionine, and threonine.

Feeding protein sources rich in amino acids but with an unfavorable composition doesn’t aid muscle building; instead, it places a burden on the body, as these amino acids must be broken down and excreted.

Moreover, it’s advisable to prioritize protein from fiber-based sources to minimize the starch content (sugar) in the feed. Examples of such protein sources include leguminous plants. The most well-known of these are lucerne, and its ‘sister’ plant, sainfoin. The latter, sainfoin, not only boasts a more favorable protein ratio with higher levels of lysine, methionine, and threonine, but it also introduces tannins into the intestine. These tannins help stabilize the intestinal environment and, in turn, enhance the overall digestibility of the diet.


If it’s not feasible to provide horses with soaked sainfoin chunks, perhaps due to the horse’s aversion to moist feed or logistical constraints, the diet can still be improved by selectively supplementing the three essential amino acids. You can purchase it directly as OKAPI Lymeth and simply mix the powder with your regular horse feed. With proper training, the appropriate muscles will become visible.