Protein Ingredients in Horse Feed

Protein (and more specifically the amino acids that make up protein) is essential to a balanced diet. It is probably one of the most referenced nutrients in horse feed, and most horse owners will know the protein content of their feed. But how do we get the protein into the feed? Sources of protein for humans may come from a juicy steak, a nice salmon filet, or a tender pork chop. We derive most of our protein from meat sources which makes sense for us since we are carnivores. The horse, on the other hand, is an herbivore; many of the types of protein that we consume as humans do not come into play in our horse’s diet. However, we do know that the horse has a nutritional requirement for protein and so when we formulate feeds we can use certain plants that are high in this particular nutrient. Some of the most popular ingredients used to add protein to horse feed are:

Soybean Meal – This is the most common form of plant protein. Soybeans are readily available throughout the country and have the highest concentration of protein of any of our plant sources, with a typical level of 44-48%. Additionally, soybean meal contains a close match nutritionally to what horses require for amino acids. Especially important in this profile is the amino acid lysine, which is essential in young growing horses.

Canola Meal – Canola meal is the closest to meeting the nutritional profile of soybean meal and has a protein content of 35-44%. Canola meal is a by-product of oil removal from

canola and has slightly less lysine content than soybean meal, but still enough to meet the requirements of horses.

Linseed Meal – this is also a by-product and is derived from the processing of flaxseed. Linseed used to be commonly fed to show horses to add shine and bloom but its popularity has waned as ingredients like rice bran and vegetable oil have taken its place. Linseed meal has a typical protein level of 33 – 35% but it has significantly less lysine than either soybean or canola meal.

As you can see, we have several options to help us meet the requirements that our horses have for protein. By adding one or more of those options to our formulas we are able to provide a diet that is balanced, healthy, and nutritious!

5 Replies to “Protein Ingredients in Horse Feed”

  1. Is whey protein not used as a good source of protein and amino acids because of the cost? Or is there a reason why whey protein is not a good ingredient to put in horse feed? And how about dried green peas? Just curious?

    1. Hi Barbara,

      Whey protein is generally a more expensive protein source for the essential amino acids (particularly lysine, methionine and threonine) required for horses than say soy protein and some of the other vegetable protein sources. Whey may also contain significant amounts of lactose (milk sugar). Published research has indicated that older horses, past the age of 3, are not able to digest lactose efficiently and have become somewhat lactose intolerant. Whey products are sometimes used in foal feeds and are generally quite palatable and well digested by the foals and young horses. When used in horse feeds, whey has to be labeled carefully as it is classified as an animal protein, which some consumers object to seeing on a horse feed label.

      Dried green peas are more commonly used in Europe than in the United States as they are not widely available as an ingredient in the U.S. They are a moderate protein source, but are low in sulfur bearing amino acids, with a fairly high starch content compared to other protein sources. There are also some anti-nutritional factors in green peas that require heat treatment to prevent them from having a negative impact on horses and other simple stomach animals if fed in significant quantities.

      I hope this has helped to answer your questions!

  2. My horse urinates a lot when given alfalfa. Is alfalfa a better source of protein than soybean meal? What makes one better than the other?

    1. Hi Linda,

      Thank you for your interesting question regarding protein quality of alfalfa compared to soybean meal and impact of alfalfa on urine output. Crude protein in feed ingredients is calculated by the amount of nitrogen x 6.25 as crude protein is about 16% nitrogen. Protein quality is determined by the quantity of essential amino acids in the crude protein with lysine, the first limiting essential amino acids, being considered first. Depending on maturity, alfalfa hay can be 17-22% crude protein as fed and .8 to 1.0% lysine. This would mean that the lysine may make up 4.7 to 4.5% of the crude protein. Soybean meals is 44-48% crude protein as fed and 2.8-2.96% lysine. This would mean that the lysine is 6.4-6.2% of the crude protein. This makes soybean meal a higher quality protein source for meeting the requirements of the horse for the first limiting essential amino acid. While good quality alfalfa hay is a good protein source, soybean meal is one of the best vegetable sources of protein for simple stomached animals because it provides high levels of lysine as well as the other essential amino acis. Regardless of the source, what we actually have to meet is the horse’s requirement, based on % in diet X intake. If you feed 20 pounds per day of alfalfa and 2 pounds of soybean meal, a lot more protein will come from the alfalfa!

      If horses consume more crude protein than needed, the excess protein is used as an energy source, somewhat inefficiently, and the excess nitrogen is converted to ammonia and excreted in the urine. This is why a horse that is consuming excess protein, regardless of source, will produce more urine and you may notice more of an ammonia smell in the stall. This is not detrimental as long as the horse has access to fresh clean water and is not at risk of dehydration. Good stall ventilation helps also!

      The ideal situation is to meet the horse’s requirement for all essential amino acids without substantial excess crude protein. When we do this, we can optimize protein/amino acid utilization for muscle maintenance and growth, hair coat quality and hoof quality.

      Best wishes,

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