Why are Amino Acids for Horses Important?

In order to fuel, repair, and recover muscle, equine diets must optimally contain a superior amino acid profile, including all 10 of the essential amino acids. Most horse owners can quickly name the crude protein level in the feed they provide their horses. But, what horse owners really need to know about is the amino acid content. Protein is made up of amino acids, similar to how a chain is made up of links. There are two basic categories of amino acids: Essential and nonessential. Essential amino acids must be provided in the diet, as the horse cannot create them on its own in the digestive tract, where the nonessential amino acids can be made. Nutrena products that include Topline Balance help to provide the right kind and ratio of amino acids in each formula.

Another key point is that some amino acids are known as “limiting” amino acids. This means that if a horse runs out of this type of amino acid, it can’t utilize any of the remaining amino acids present in the feed. 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 horses, the first three most-limiting amino acids, in order, are lysine, methionine and threonine. Generally speaking, if these three amino acids are present in sufficient quantities, the ingredients used also provide the remaining amino acids in sufficient quantities. It is increasingly common to see these three amino acids listed on the guaranteed analysis of horse feed tags, as it is an indication of the quality of the protein sources and the balanced nature of the feed.

If you are looking for a feed that may help impact topline, be sure to look at the guaranteed analysis on the feed tag. In specific Nutrena feeds – SafeChoice products, ProForce products, and Empower Balance – the amino acid levels are called out and guaranteed on the tag. The amino acids included in Nutrena’s Topline Balance products are included in specific amounts and ratios. Research has shown that this specific combination and type of amino acids help to support a healthy topline when fed correctly.

Guaranteed amino acids on the tag is a good starting point. You then need to let the horse tell you if the feed is working by regularly evaluating and noting changes in topline condition.

Does My Horse Need a Diet or Exercise Change?

I recently taught an Equine Nutrition class to a group of seniors at an area college.  Our focus for the classroom lecture was dietary assessment by body condition scoring, weight and topline evaluation.   After the lecture I conducted a lab to apply hands on practice of what we had just reviewed.

One of the students asked if we could evaluate her horse during the lab session. The evaluation proved to be a classroom classic. The horse was a 4 year old Warmblood gelding. He was 17.1 hands and 1350 pounds. The horse at first glance appeared to be round and in good flesh, but as I ran my hands over his withers and back you could feel a lack of muscle and coverage.hand feeding red size

I asked the student what the horse’s current diet consisted of, she replied 20 pounds of first cutting hay per day and 8 pounds of locally grown oats. The calorie content of the diet appeared to be sufficient, however the amino acid balance was lacking. The student also mentioned she had her saddle recently refitted and the chiropractor out because the horse was having back issues.

With the move to college, the horse’s workload had increased and the need for additional fortification was obvious. I suggested that the student purchase a ration balancer to balance the needs of the young horse’s diet and help replenish his topline.

One of the students in the lab then challenged my recommendation.  She stated that she was an Equine Physiology major and felt my diagnosis was incorrect. She felt that by working the horse in a more collected manner, engaging his hind quarters and coming up under him would help to strengthen and develop his topline. She thought he looked fat and did not need to change his diet.

I went on to explain that the horse’s current diet was similar to a young child that would be on a straight rice diet, which is deficient in amino acids. You would see a round abdomen, but lack of muscle mass. If that child were getting ready to compete in a marathon, I doubt running extra laps would increase muscle mass, unless we supplemented the diet properly.

Again, your horse will tell you what is lacking in his diet, if you just take the time to look.

What are Essential Amino Acids in Protein, and Why Do They Matter?

Nutrition articles frequently refer to protein quality and essential amino acids. When we use the term crude protein, we are essentially talking about a calculation based on measured nitrogen. Protein is about 16% nitrogen by weight, so if we measure the amount of nitrogen and multiply it by 6.25, this gives us a measurement of crude protein. It does not tell us anything about the quality of the protein. If you tested pure nitrogen this way, it would be 625% protein!

Digestible protein is that amount of the protein that is actually digested by the animal. In an over simplified example, if you fed 100 grams of protein and measured 50 grams in the feces, the protein would be 50% digestible.

What is really important to simple stomached animals (horses included) is the content of essential amino acids in the protein. We commonly talk about 10 essential amino acids (EAA), the amino acids that must be in the diet as the animal cannot synthesize them. These are:

  • Phenylalanine
  • Valine
  • Threonine
  • Tryptophan
  • Isoleucine
  • Methionine
  • Histidine
  • Arginine
  • Leucine
  • Lysine

A common memory aid in many nutrition texts books is to use the first letters of these 10 as PVT TIM HALL. (All of you who had a non-ruminant nutrition course still remember this acronym!)

The other 12 amino acids can generally be synthesized in the body and do not need to be in the diet, although there must be a supply of appropriate substrate to produce them. Animal nutrition text books cover this topic in excellent detail.

Limiting Amino Acids

Limiting Amino Acids

When we talk about limiting amino acids, these are the essential amino acids most likely to be restricting the use of the total amount of amino acids present. In most species, lysine is the first limiting amino acid, with methionine and threonine close behind. We commonly talk about amino acids as the building blocks of protein. If you are once you run out of an essential amino acid, you cannot build any more animal protein and the rest of the amino acids are used inefficiently for energy.

If you have a horse on a diet that is calculated to have adequate “crude protein”, but essential amino acids are not present, the horse simply cannot use the protein to build and maintain muscle, hair, hoof and skin and you will see changes in the appearance of the horse, such as loss of muscle mass, rough hair, scaly hoof surface.