Feeding protein to horses

Many horse owners are scared of protein and believe it makes their horse crazy or hot. Some think it causes laminitis and growth problems in young horses or even leads to kidney damage. In reality though, protein does not cause any of these issues. As a matter of fact 15% of your horse’s total body mass is made up by protein and can be found in the muscles, skin, hair and hooves. Unfortunately protein is quite misunderstood, which is a real problem as it is critically important. In order to provide adequate dietary protein, it is important to have an understanding of how protein is digested and absorbed, the different dietary sources of protein available to the horse and the protein and amino acid requirements for horses of various ages and physiological states. We have broken this article up into 4 sections to give you a better understanding of the role of protein in your horse’s diet.

Why does my horse need protein?

Some of the key functions of proteins in your horse’s body include providing structure, nutrient transport in the blood stream, nutrient transport across cell membranes, regulation of metabolic function, as a component of the immune system and to act as a buffer to minimize fluctuations in body pH. Protein assists in tissue repair and growth, hence the amount of protein required in growing, pregnant, lactating or heavy exercising horses is increased.

Protein Digestion

Proteins are composed of units called amino acids. Although there are 21 different amino acids that are needed for protein synthesis, several can be made by the tissues of the body. Amino acids that must be provided in the diet are referred to as indispensable(essential) amino acids, and amino acids that the animal can make through its own metabolic pathways are termed dispensable(non-essential) amino acids. In order for your horse to be able to utilize dietary protein throughout his body they must first be digested into these individual amino acids. The digestion of protein begins in the stomach, through to the small intestine which results in the end product the free amino acids. These are then available for absorption into the blood stream and used for various functions throughout your horse’s body. The absorption rates of individual amino acids are highly dependent on the protein source.

How much protein does my horse need?

Before we can answer that question we first have to understand that the absorption rates of individual amino acids as discussed before in your horse and therefore, their efficiency is highly dependent on the protein source your horse receives. In practical terms this means you should not just look for protein quantity in your horse’s diet, but also for protein quality. The quality of a dietary protein is determined by the amount and proportion of essential amino acids it provides. To increase the quality of protein in commercial horse feeds the amino acids Lysine; Threonine and Methionine are most likely to be added. Unfortunately, there is no definite indicator to detect a dietary protein deficiency, however, visible withers and hip bones and lacking muscle mass over your horse’s back and rump, might indicate that better quality protein is needed along with a supportive exercise regime. Other symptoms of dietary protein deficiency may include general non-thriftiness, depressed feed intake, weight loss and poor hoof and hair coat quality. If an essential amino acid is deficient in growing horses, it is reflected by lower rates of average daily gain. Other studies have also reported reduced milk production, increased weight loss in mares and reduced rates of foal growth if insufficient dietary protein is provided during lactation. Growing horses and lactating mares have the highest protein requirements of all horses. If we use a 500kg horse in light work, we are looking at a daily protein requirement of 700g versus 1500g for a lactating mare, which is more than double the requirement. Furthermore, athletic horses that do not consume enough essential amino acids to maintain their increased muscle mass or replace nitrogen losses in sweat will begin to deplete the plasma amino acid pool or lose muscle mass, resulting in increased nitrogen excretion.

Protein Sources

Not all protein sources are the same – some are of a higher quality than others. Quality of a dietary protein is determined by the amount and proportion of essential amino acids it provides. Your horse consumes a variety of ingredients from roughage to grains that each have varying levels of protein quantity and quality.

High quality protein - Sources high in quality protein are legumes such as soybeans, tick beans, lupins and seed meals from sunflower and canola. I have to point out though that the amino acid profile of soybean meal is superior to most other seeds and beans with a protein content of 44-48%. HYGAIN^® GROTORQUE®is a textured feed that provides high quality protein levels. Moderate - Low quality protein - Cereal grains are incorporated into horse diets for energy, but they do provide protein and some amino acids as well. Cereal grains do not contain high quality protein. Consequently grain by-products often contain moderate or low quality protein, even though they may be relatively high in crude protein. Therefore the amino acid content of by-product feeds should be considered when they are incorporated into horse feeds, especially if their inclusion reduces the use of ingredients with higher quality protein. Roughage - Last but not least roughages are important components of your horse’s diet and can be an excellent source of protein and amino acids. However, the down side is that roughages can vary extremely in their protein and amino acid content. Legume forages will usually exceed a protein concentration of 14%, which is higher than most grass hays. Lucerne for instance is a high quality source of protein due to its high lysine levels.

Summary

Protein is a very important nutrient in your horse’s diet and was derived from the Greek word proteos, meaning of primary importance. Remember, the protein requirement of your horse is dependent on his physiological state and his activity level. Make sure your horse receives sufficient levels of quality protein to avoid muscle loss and poor hoof and coat quality.