The Manual of Horsemanship, The Official Manual of the Pony Club – page 180, says the following:

Hi Alan

Proteins are for body building and tissue repair.  They are made up of a number of amino acids, about half of which can be formed within the body.  The other half, ‘essential amino acids’, must be provided in the diet.  Proteins are found in varying degrees in all foodstuffs and the ‘essential amino acids’ in cereals, particularly oats, are sufficient for the horse in normal work.  Peas, beans, Lucerne and soya meal all have a high proportion of the ‘essential amino acids’, but they should be fed with caution, and only to horses doing very hard work.  Proprietary mixes and cubes contain appropriate amounts.  As the workload increases, so do protein requirements –whether for the demands of high performance or for pregnancy and lactation.  Energy food must also be increased so that the balance of protein and energy food is maintained.

-          Lack of protein results in poor growth, poor performance, lack of appetite and condition, and a poor supply of milk in a brood mare.

-          Excess protein is dangerous.  It causes body and mental stress; overworks the kidneys; and can poison the whole system.

So, yes this quote does not really help us with the quantity or the amount.

The BHS Complete Manual of Stable Management by Islay Auty FBHS – page 162, says the following:

Protein

Suggested percentage of protein in total ration:

-          Light work: 7.5 – 8.5%

-          Medium work: 7.5 – 8.5%

-          Hard work: 8.5 – 10.0%

-          Strenuous work: 8.5 – 10.0%

Suggested protein percentages required for broodmares and young stock:

- Pregnant mares: 8 – 10%

- Mares in last three months of pregnancy: 11 – 13%

- Lactating mares: 14% gradually decreasing to 12%

- Foals not receiving enough milk or spring grass: 16 – 18% in a compound ration.  On good grass with sufficient milk from their dams no extra food is necessary.  (Thoroughbreds will require special consideration, especially if bred for flat racing.)

- Weaned foals 6 months old: 14.5 – 16%

- Yearlings 12 – 18 months old: 12 -14%

- Two-year-olds: 10 – 12%

- Three-year-olds: 8.5 – 10%

NB:  There is some evidence that over feeding foals and yearlings may cause epiphysitis and/or contracted tendons.  The significance of excess protein, excess energy and/or imbalanced minerals is not yet resolved but must be important as distinct from just one nutrient being blamed.

Page 143, says the following:

Protein is a complex organic compound containing nitrogen.  Different proteins are formed from varying combinations of twenty-two amino-acids and their derivatives.

Protein is builder; it is necessary for growth and replacing wastage.  It is made up of chains of amino-acids linked together.  Some of these amino-acids can be synthesised (made) by the horse.  Others are made by the micro-organisms in the gut.  However, others known as essential amino-acids must be included in the diet.  An ordinary hay/cereal ration is low in these essential amino-acids, so for growing or working horses, additions should be made to the ration.

Lysine, methionine and tryptophan are three of the essential amino-acids, which are not available in ‘straight’ grain feeds.

Foods that are high in lysine are: 

-          Peas and beans, including soya-bean meal

-          Dried milk pellets (not suitable source for adult horses.)

-          Fish meal

-          Lucerne/alfalfa.

Not all high protein foods have easily digestible protein.  Reputable compounders making up a mix usually ensure that the protein is digestible.

Some Nutritionists maintain that the total percentage of digestible protein in the ration should not be over 10% except for lactating mares, foals and young stock.

The protein levels will naturally alter with the changes in the quality of cereal fed.  There is no evidence that athletic horses require high protein supplements although individual National Hunt and three-day event horses might.  In fact it is thought that the overfeeding of protein to competition horses can be detrimental to their performance.

As these two quotes are saying protein is important to do muscle building but there is something they are not saying and that is the protein percentage of 10% yes is correct but it also depends on the breed of horse you have.  Thoroughbreds can only work with a 10% and Warmbloods may need a 12 %.  But, don’t exclude the horses temperament because that also plays a huge a factor as well as conformation.

If you are still having a problem, please try and find a company who has a nutritionists to come a visit you, i.e. Spurwing horse feeds.

I hope all this info will help you to help your stead.

Kind regards,