Horses from all disciplines need to build muscle. Athletic horses need appropriate muscle mass to support their rider’s weight, perform the task at hand, and protect their joints and support soft tissues.
What are muscles made of?
Muscles are made of large amount of protein, water, and salt. Proteins are made up of amino acids which can be classified as essential, non-essential, and conditionally dispensable. An essential amino acid is one which the horse must consume in its diet (such as Leucine, Lysine, Methionine, Phenyalanine, and Threonine), while it can synthesise non-essential amino acids in its body (including Aspargine, Aspartate, and Glutamate). A conditionally dispensable amino acid is one which the horse can make however its production can be reduced or stopped in certain conditions, such as when the horse is sick (i.e. Arginine, Cysteine, and Glutamine). The most important essential amino acid is lysine, as this is one of the amino acids most abundant in muscles but is also known to be the primary limiting amino acid which means that if it is not present in sufficient quantities, protein synthesis in the body (new muscle growth) will be limited. Although more research is needed, it is believed that threonine and methionine are also important limiting amino acids.
But don’t be fooled into thinking that amino acids are all about building muscle! Enzymes, antibodies, haemoglobin, cellular receptors, cytokines and many hormones are all synthesized from amino acids. Next to water, protein is the most abundant substance in all body tissues from the brain to the hoof!
Protein in the diet.
What is important to remember is that the source of the amino acids doesn’t matter, however the amount of different amino acids in different types of protein varies, and so this is what should be considered when formulating a horses diet. Most horse feed manufacturers give the crude protein % however this does not indicate how much of the protein is made up of essential amino acids such as lysine. As an example, soybean contains 37% crude protein and cottonseed meal contains 36%. If these levels were indicated on a feed bag it would look as though they both contained a similar amount of protein, however if we look at the amount of lysine in each of these, soybean contains 23.3g/kg and cottonseed meal contains 14.7g/kg. Based on this information, feeding soybean would be far more beneficial in terms of amino acids and protein synthesis than cottonseed meal!
Protein requirement determined by horses stage of development. Approx 1.26g of crude protein per kg bodyweight is required for the average horse in work (more is required for young horses, during pregnancy etc). This works out to be around 630g crude protein per day for a 500kg horse. It’s important to remember that protein is available in grass and hay, so you don’t need to provide this full amount in the horses grains/pellets/supplements. It’s also important to remember that this is the total amount of protein required, not the amount of individual amino acids. Your horse needs a variety of amino acids in its diet.
What about supplementing amino acids?
Supplementing amino acids can be beneficial to many horses, especially those in work or who are on poor pastures. Dr Eleanor Kellon recommends 10 – 20 g lysine, 5 – 10 g methionine and 2 – 4 g threonine per day for the average horse. Another important thing to remember is that it’s extremely difficult to overdose the amount of protein given, as any excess will be excreted in the urine. Supplementing these three essential amino acids works out to be a relatively cheap way to increase the amount of these limiting essential acids in the diet to ensure they are getting sufficient amounts. There are many places to purchase these but this is one that you could purchase pre-made: https://balancedequine.com.au/product/equine-amino/
General nutrition also important as well as protein intake. If the horses dietary intake doesn’t meet its requirements, protein will be used as energy rather than for building muscle. So while supplementing the amino acids mentioned above is great, if the rest of your horses diet is poor, you won’t see the best results.