Switching on muscle building
I hope you find this blog post helpful! If you want a custom diet specific to your horse, click here.
P.S. We love AI, but this content is 100% written by a human. 💕
Author: Dr Nerida McGilchrist | PhD Equine Nutritionist and Founder of My Happy Horse
As horse owners, one thing we LOVE is when our horses are well muscled! It looks beautiful AND it is also very functional!
Our horse’s need their muscles for speed, strength and agility. Muscle also provides stability and balance and a whole host of really important metabolic functions like the storage and utilization of glucose.
Building blocks of muscle
Muscle is made from protein. And protein is made from amino acids. So to build muscle, a horse needs access to ALL of the amino acids it needs to put muscle together.
Muscle protein synthesis also literally needs to be switched on before anything will happen. And there is only one nutrient that can make this happen!
The muscle building switch
Back to the amino acids for a minute… There are 20 amino acids. Ten of them we call non-essential amino acids as our horses can make them for themselves, so we tend not to pay these a whole lot of attention in general nutrition.
The other 10 amino acids are called the essential amino acids, because they must be provided in the diet.
Within this group of essential amino acids there is a group called the ‘Branch Chain Amino Acids’ or the BCAAs, which includes leucine, isoleucine and valine.
In human muscle, BCAAs make up around 18% of the amino acids in our muscle protein, making them super important when it comes to building extra muscle mass!
AND leucine has the particularly important role of SWITCHING ON muscle protein synthesis. Research in this area shows that it appears it is almost singularly responsible for doing this.
The 4 requirements for building muscle
All muscles require four things in order to build. These are:
Work! Muscles won’t grow unless they are given work to do.
Leucine. This branch chain amino acid switches on muscle protein synthesis.
A ready supply of all of the other amino acids, and particularly the essential amino acids. Between work and leucine, muscles are stimulated to grow. They then need a ready supply of all the amino acids they need in order to actually build new muscle.
A balanced diet that is meeting all requirements for vitamins and minerals. Deficiencies in nutrients like zinc and vitamin E will slow or stop muscle building and can even contribute to muscle wastage!
Which feed ingredients are the best source of leucine?
Leucine has the extra important role of switching on the muscle building process, making it important that we ensue there is plenty in the diet.
There are multiple feed ingredients that are a good source of leucine. Here is a list of the best ones:
Whey Protein Concentrate. This ingredient contains around 80% crude protein (depending on the brand) and has over 10 grams of leucine per 100 grams. Certainly the richest source of leucine (and all of the other important essential amino acids) you can get. It works, but it is not cheap. If you use whey protein be sure to use it very strategically and feed it to your horse within 15 to 30 minutes of finishing a work session.
Maize (Corn) Gluten Meal. This byproduct of maize is around 62% crude protein and contains almost as much leucine as whey protein concentrate making it super useful for boosting leucine intakes! It is however a relatively poor source of the essential amino acid lysine, so needs to be fed in conjunction with other high quality sources of protein like soybean.
Soybean. Soybean is well known to be the richest plant source of essential amino acids, including leucine. Soybean meal contains 47% crude protein and will give you 3.5 grams of leucine per 100 grams of meal. Full fat soybean is around 36% crude protein and will give you about 2.7 grams of leucine per 100 gram serve.
Brewers Yeast. Brewers yeast is also a handy source of leucine. It contains 50% protein and will give you 3.2 grams of leucine per 100 gram serve. Like whey though, it’s a relatively expensive option.
Other common feedstuffs and their protein and leucine content are shown in the table below.
| Ingredient | Crude Protein (%) | Leucine (g/100 g serve) |
|---|---|---|
| Whey Protein Concentrate | 80 | 10.8 |
| Maize (Corn) Gluten Meal | 62 | 10.1 |
| Soybean Meal | 47 | 3.5 |
| Brewer's Yeast | 50 | 3.15 |
| Full Fat Soybean | 36 | 2.7 |
| Lupins | 34 | 2.4 |
| Peas | 21 | 1.5 |
| Chick Peas | 20 | 1.5 |
| Alfalfa/Lucerne | 17 | 1.1 |
| Rice Bran | 15 | 1 |
| Sunflowers | 16 | 0.9 |
| Wheat Midds | 15 | 0.9 |
| Oats | 9 | 0.7 |
There are also BCAA supplements available that can be used. However, if you feed diets that already contain naturally high levels of these amino acids, for most horses, this is enough!
BCAA supplements can however be super useful for muscle recovery, but we will cover that another time!
Happy muscle building!!
If you have any questions about protein, amino acids or building muscle, be sure to ask Dr Nerida AI!
And download the free MyHappy.Horse app and have it create beautifully balanced muscle building diets for your horse today. 😊
About the Author
Dr Nerida McGilchrist
Dr Nerida McGilchrist is an Australian equine nutritionist with a PhD and over two decades of experience. As the founder of Equilize Horse Nutrition, and advisor to some of the world's largest nutrition companies, she’s built an international reputation for blending science with practical solutions. Now, she’s bringing her expertise to My Happy Horse to make advanced nutrition accessible to all.