Fact or Fiction!


Too much protein in the diet results in an unmanageable ‘fizzy’ horse and causes allergic skin reactions, laminitis and tying-up.

I wonder how many of us have heard one or more of these anecdotes at one time or another.

Protein has received a lot of ‘bad press’ in the past and there are those who still believe that feeding a diet which is rich in protein will result in many of the situations above. We have put together a fact or fiction guide to answer some of the most commonly asked questions concerning protein.

What is Protein ? Protein is made up of building blocks called amino acids, analogous to beads in a coloured necklace, where each coloured bead represents a different type of amino acid.

Why do horses need protein ? The amino acids in proteins are needed as raw materials for tissue growth and repair and for the production of enzymes, hormones and other substances involved in body metabolism. It is the amount of protein provided daily in grams which is important and grass, hay and hard feed fed will contribute to this.

Can I overfeed protein ? All horses need a certain amount of protein in their diet, which will depend on their, age, stage of growth and exercise regime. The amino acids produced, from any protein fed above this requirement, are re-processed. The nitrogen containing part is excreted in the urine and the other part can either be converted to fat or used as energy.

Will a protein rich diet make my horse ‘fizzy’?

In most cases this will depend on the energy content (MJ / kg) of the ration you are feeding and not the protein content. The source of the energy may also have some influence, i.e. quick release energy’ from cereal starch or ‘slow release energy from fibre or oil. However, you will notice that most feeds that are rich in protein are also higher in energy. The notable exception to this are alfalfa based feeds, such as Dengie Alfa-A, which has a protein content of 15% but an energy content of only 9 MJ/kg. In most cases, the ‘fizz factor’ is as a result of a miss-match between the amount of energy fed (MJ) and that needed for daily life, rather than the amount of protein in the diet.

Feed % Protein Energy (MJ/kg)
Dengie Alfa A 15 9
Low Energy Mix


Competition Mix 11 11.6
Stud Mix 16 12.5
Racehorse Cubes 14 13

Does too much protein cause laminitis ? When laminitis is attributed to the diet it is more likely to be as the result of over feeding soluble carbohydrate or sugars, especially in ponies which are overweight.
Will my horse ‘Tie-up’ if I feed too much Protein ? The current thinking on ‘tying up’ is that excess energy or an imbalance in the body’s electrolyte and or mineral intake may be implicated.
Is my horse allergic to Protein? Probably not protein per se. Protein bumps’ or urticaria, when caused by the diet, are probably the result of a sensitivity to a particular source of protein e.g. barley, oats or beet pulp.

So as you can see protein is not always the ‘Bad Guy’ and forms a very important part of our horses diet. But how much protein should we be feeding ? An average horse in light work will need about 750g of protein per day. This requirement would easily be met by 8kg of average quality hay (7% protein) together with a couple of kilos of a course mix (9-10% protein) or just over a kilo of an alfalfa chaff (15% protein).

The protein requirements of breeding stock and youngsters, as well as some older horses are higher than that needed for maintenance and light work. Most stud mixes, foal and yearling feeds and feeds designed for the veteran horse or pony, usually have a higher inclusion of protein.

However, as with most other things it is not just the quantity that is important but also the quality. A quality protein source will be easily digested and have an amino acid profile similar to that needed by the horse.

Both Soya and alfalfa are good sources of quality digestible protein. This all sounds quite complicated but in fact, most of the hard work has been done for us. Most feed manufacturers produce feeds designed specifically for different equine lifestages and take account of their requirements for growth, exercise and even old age. When fed with good quality forage most of these feeds will more than adequately cover the protein requirements of all our horses throughout their lives.

Dr Catherine Dunnett

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Updated: October 2005.