After writing about dietary energy last week, it seems sensible this week to write about dietary protein, since protein is another nutrient that is surrounded by myth both in the horse world and the human sports world.

Protein is made up of chains of amino acids, and both horses and humans have a requirement for amino-acids, rather than actual protein. Amino acids are nitrogen-containing compounds that are built into proteins by body cells. Proteins make up over half of the structure of body cells, are enzymes, messengers, transporters, contractile and fibrous tissue elements, and have roles in immunity, fluid balance and pH balance. Some amino acids can be made in the body from others, and these are called ‘non-essential’. Those that cannot be made and must be supplied in the diet are called ‘essential’ and it is the content of these in a protein that reflects its quality. The quality of protein is more important than quantity.

Soya beans are the best quality protein for horses, due to their high lysine content.
Soya beans are the best quality protein for horses, due to their high lysine content.

Protein tends to be declared as a percentage of a feed or supplement, but it’s the actual amount in the total diet that matters. So in addition to the percentage protein of a feed or supplement you need to know the amount of that product that you feed.

Protein requirements are generally lower than most people think, and it’s only during growth, the final few months of gestation and the first few of lactation that protein requirements are relatively high. Even hard working horses do not need high levels of protein because it is not a substantial source of energy for them. If hard working horses have their energy requirements met from a high quality diet, they will usually receive enough protein. Sick horses and those healing after trauma including wounds require adequate protein for recovery, and wound healing can be delayed by a protein-deficient diet.

Lactating mares have the highest protein requirements of all classes of horse.
Lactating mares have the highest protein requirements of all classes of horse.

Protein is not heating, it will not fizz your horse up, it does not cause laminitis and it does not cause your horse to tie up. Protein status is not easy to assess from looking at your horse unless they are very deficient. Providing that the quality of protein in your healthy horse’s diet is good, and you are fulfilling their energy requirements, you can rest assured that they are receiving enough protein.

Horses who could lack dietary protein include:

  • those on weight loss regimes, specifically with very mature hay, straw or 10 hour-plus soaked hay
  • hard working very good doers who require less energy than usual
  • inappetant sick or healing horses who are eating less than 1.8% of bodyweight per day

In the above cases, the quality of protein needs to be high in order to meet requirements. Horse feed ingredients that are rich in good quality protein are the oilseeds and beans, including soya bean, sunflower, linseed and rapeseed. Soya bean meal has the best quality profile, with high levels of lysine, the ‘limiting’ essential amino acid. Grass, good quality grass hay and alfalfa hay and chaff are good protein providers. Compound feeds are formulated to contain good quality protein so the examples above should be fed an appropriate compound feed at the full recommended amount. Pelleted balancers are useful to supply good quality protein without adding too much extra energy.

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About Clare MacLeod

Clare MacLeod MSc RNutr is one of the UK’s few registered independent equine nutritionists who also has expertise in health and fitness. She advises private and commercial clients in all sectors of the horse world and is a hands-on horse owner herself. Clare is passionate about correct nutrition as a foundation for good health, without which peak fitness is not possible. She states “Good nutrition isn’t everything, but there’s nothing without it”.