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Protein in your horse’s diet

Unfortunately, protein is often cast as the villain, but it is actually vital for good health. It is found in all tissues in the body and enzymes, hormones and antibodies are also made of protein. The building blocks of protein are amino acids, some of which have to be supplied in the diet because the body cannot make sufficient quantities to meet requirements. Those that have to be supplied in the diet are termed essential amino acids and the ‘quality’ of a protein is often measured by the levels of essential amino acids it contains.

Lysine is the only amino acid, essential or otherwise, for which the horse’s requirement has been determined. It is particularly important for youngstock because a deficiency will limit growth and development.

Alfalfa as a source of protein in horse feeds

Alfalfa is a member of the legume family, so possesses the ability to ‘fix’ nitrogen from the atmosphere and incorporate it into the plant. Along with soya, which is also a legume, alfalfa is one of the most commonly used sources of protein in horse feeds.

The key features of the protein in alfalfa are:

  • Most of the protein in alfalfa is found in the leaf. In fact, the leaf contains two to three times more protein than the stem.
  • The level of quality protein in alfalfa is very good, with lysine at 0.83% compared with wheat at 0.4% on a dry matter basis.
  • 3kg of Alfa-A Original provides a 500kg horse in light work with 65% of its crude protein and 62% of its lysine requirement. NB: Grass and hay/haylage will usually supply the rest, so a broad-spectrum supplement is all that is needed to provide a balanced diet for most horses and ponies.

Dispelling myths about protein in horse feed

It has taken some time, but there is now fairly extensive research vindicating protein, which raises the question: why was protein ever thought to be the cause of so many problems. The explanation might well lie with the laws governing the nutritional information that has to be listed on every bag of horse feed.

Because the level of protein has to be declared on a bag of feed and the starch level doesn’t, protein has often been used as the measure of the ‘richness’ of a feed. With traditional cereal-based compound feeds such as mixes and cubes, it usually follows that the higher the protein level, the higher the starch level as the feed provides more energy for a harder level of work. If high protein (and starch) feeds are being fed and a problem such as laminitis or colic ensues, it is fairly understandable that protein is believed to be the cause because this is the nutrient that the horse owner knows has increased when they look at the back of the bag. Until changes to legislation are made, it is likely that some horse owners will continue to blame protein for a number of problems.

Some of the diseases and problems that protein is wrongly blamed for include:

  • Laminitis – most laminitis cases results due to an underlying endocrine problem including EMS or PPID. Horses prone to laminitis need to have the amount of sugar and starch in the ration restricted, not the amount of protein.
  • Muscle problems– research has shown that high-starch diets and not excessive protein intake are a contributing factor to muscle-related problems now referred to as ERS.
  • Over-excitable behaviour – protein is rarely used as an energy source by the horse and over-exuberant behaviour is more likely to be caused by an increase in energy intake, of which the horse owner might not be aware. The levels of energy in grass and hay/haylage vary throughout the year and, even if the horse consumes the same amount of forage, the energy intake might still increase through ‘hidden’ energy.

Where do I get more information on protein levels in my horse’s diet?

Because feed manufacturers have to declare only the level of crude or ‘total’ protein on a bag, this doesn’t tell you much about the levels of essential amino acids in the feed. Most manufacturers will be able to tell you this information if you request it directly. If you would like a personalised feeding plan for your horse, including more information on key essential amino acid levels, please telephone the Dengie Feedline on 01621 841188 or email