Most horse owners understand the importance of protein in a horse’s diet.  Most understand that protein is used for growth and the repair of muscle and tissues.  Few however can tell you what protein is actually made of. 

Protein is made up of Amino acids much like a wall is made of bricks. There are 22 Amino acids that constitute protein in your horse.  A horse needs all 22 to build proteins in his body. Horses get these Amino acids two ways; they make them in their body or they get them from their food. 

Of the 22 Amino acids there are 10 that are called essential.  The essential Amino acids come from food.  Essential Amino acids must be provided in the diet because the horse cannot manufacture them on their own in the digestive tract. The importance of providing these essential Amino acids can be better understood when we look at the jobs they do:

Lysine- Muscle development and bone growth plus stimulates gastric juices.

Methionine-  Hair and coat growth, prevents deposits and adhesion of fat in liver, selenium absorption, antioxidant and anti-arthritic.

Threonine- Enhances growth and food efficiency, produces adrenaline, and is a precursor to thyroid hormones.

Arginine- Releases insulin and growth hormone, nutritional aid in cancer therapy, fights tumor growth, and boosts T-cell production.

Histidine- Maintains plasma, hematocrit and serum albumin, releases histamine, controls pain, anti-arthritic. Also stimulates stomach acid secretion and improves appetite.

Phenylalanine- Produces epinephrine and norepinephrine and acts as an antidepressant.

Tryptophan-  Component of serotonin so acts as a mood stabilizer.  Precursor to niacin, and may aid in blood clotting .

Valine- Regulates protein turnover and energy metabolism with leucine and isoleucine. Is vital for muscle coordination .

Leucine- Keeps muscle protein from degrading.

Isoleucine- Forms hemoglobin and fights nervous system degeneration.

Among the 22 Amino acids there are some that are referred to as “limiting” Amino acids.  These are the foundation Amino acids meaning that if a horse doesn’t have enough of a “limiting” Amino acid it can’t utilize any of the remaining Amino acids present in its diet.  The Amino acid whose supply runs out first and “limits” protein synthesis from proceeding is considered the first “limiting amino acid.”

But there is more, if the horse has enough of the first most limiting Amino acid, but then runs out of the second most limiting Amino acid, it can’t use the remaining amount of the third most limiting, and so on.  In other words, if the foundation isn’t there you can’t build the wall.

There are actually three Amino acids in the equine diet that are considered limiting; lysine, methionine, and threonine.  Of the first three, lysine is the most limiting Amino acid. In other words, it is the one most lacking in the equine diet.  Many feed tags have a guarantee for lysine because of this. But therein lies the problem.

Note: This feed label is for  performance, breeding and growing horses so horses that need the highest and best quality protein!

Here is a different tag with all three limiting Amino acids guaranteed.  This is a must to assure you get what you pay for in your grain. You’d be surprised how many expensive feeds don’t have these very important guarantees even though you might think they do.  Check your tag.

As we saw before, it is really important that all three be present in sufficient quantities.  If they are you can feel sure that the ingredients used to provide them also provide the remaining Amino acids in sufficient quantities.  Therefore, it is very important (especially in performance, breeding and growing horses) that all three are listed in guaranteed analysis of your horse feed tag, as it is an indication of the quality of the protein sources and the balanced nature of the feed.  You will learn more about this when we get to “G”.

When your horse ingests protein, the Amino acids that make up protein are broken up by the enzymes and acids in its digestive tract, specifically the “foregut” (stomach and small intestine).  Each Amino acid is absorbed through the wall of the small intestine and into the bloodstream via the liver. The Amino acids then travel to the areas in the horse that needing growth and/or repair.

Hope this helps you understand a bit more about protein.

 ~Peace and good feed,

The Nerd

Hope this helps your