In science lessons we are taught that proteins are ‘the building blocks of life’, essential for growth and repair. This is true for us and also true for our horses. Proteins consist of long chains of amino acids, 10 of which (there are 22 in total) cannot be synthesised by the horse and therefore must be provided by the diet. This considered, can protein really be responsible for as many problems as is often believed?
Too much protein is often thought to cause/ contribute to conditions such as laminitis, colic and tying up. However, years of research has shown that nutritionally, excess starch and sugar (including fructan in grass) is often responsible and not protein. If undigested in the small intestine, starch and sugar is rapidly fermented in the large intestine resulting in the production of lactic acid. This causes damage and death to gut bacteria which can consequently lead to conditions such as laminitis and colic. Whilst many factors can have an effect nutritionally, it is also high levels of starch and sugar that can cause/ exacerbate excitability. So if research tells us otherwise, why is protein often deemed the culprit?
One possible explanation could be the law surrounding feed labels. Protein content must be declared on feed labels but for many years, this was not the case for starch (must now be declared if making a claim i.e. ‘non-heating’). Consequently, if moving to a higher energy feed resulted in a change of behaviour or episode of laminitis, many owners may have thought the increase in protein (and not the hidden increase in starch) was responsible.
Aside from the conditions above, lumps and bumps on the skin and filled legs are the most common reasons owners ask me for advice on low protein diets. Although traditionally diagnosed as ‘protein bumps’, in many cases, lumps and bumps are not diet related. True feed allergies are very rare are the result of a specific type of protein and therefore reducing the amount fed would be unlikely to help (see previous blog on allergies).
When not accompanied by heat or lameness, being stabled for longer periods i.e. overnight is generally considered to be one of the most common causes of filled legs. In fact, there is no reason why excess protein should cause filled legs and therefore any accompanying feed changes are likely to be coincidental.
Although there are some clinical conditions which do demand a low protein diet (namely liver and kidney damage); protein is essential for growth, life and health and certainly does not deserve the bad press it often receives.