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A nice mash now and then? Better not...

  • Veterinary

by Emanuela Valle, veterinary, Prof. at Torino University


Old horselore says a mash a week is a good thing to refresh the horse’s gut. However, many of us have seen the real effects of this ‘tradition’ the following day: very often the horse will have runny droppings, and anyone who thinks this is beneficial for the prevention of constipation is sadly mistaken.


Often after eating an occasional mash a horse will have diarrhea the following day


This is due to an imbalance within the gut which affects its micro-organisms and therefore the consistency of the faeces.

So, any sudden changes in diet, such as that of the occasional bran mash, possibly also containing cooked cereals, is absolutely not a healthy thing for a horse, and there are various reasons why this is so – let us examine each of these.

  • Sudden changes in diet: above all, if the horse does not eat the main ingredients of the standard mash (barley, bran, perhaps oats and corn) regularly, we can safely assume that its population of gut micro-organisms are not accustomed to these foods, and therefore this will create an imbalance which does not have a positive effect on gut health.
  • Excessive amounts: if the usual quantity of mash is fed, following traditional ‘recipes’ (for example 1.5kg of barley, 1 kg bran, for a 500kg horse) we need to be aware that we are surpassing the digestive system’s ability to handle that amount of starch. This means that a lot of starch arrives in the large intestine, creating abnormal levels of fermentation which results in precisely the laxative effect we noted above.


Cereals are very high in starch, which the horse is unable to digest easily. This is why we need to be very careful with the amount of cereals we feed.


  • Imbalance: cereals, and in particular bran, have an uneven calcium-phosphorus ratio, with more phosphorus than calcium, and in the long term this will cause an imbalance in the minerals absorbed, and this in turn has an effect on the mineralisation of the bones.  For example, horses with abnormally large heads were a relatively common sight in the past, due to a disease, seen in particular among horses belonging to millers, since they received daily rations containing a lot of bran, a by product of the milling process. These horses, fed on abundant quantities of bran, presented

(photo: Veterian Key)


  • Lack of fibre: a mash based on cereals contains less than 10% of fibre, while forage contains at least 30%.  Therefore, if, following a colic episode, we feed a cereal-based mash to help the intestine recover, we should be very much aware that we are not helping in the least.


Alternatives to mashes

If we really want to help the gut to function better, and to absorb water, we have to look at fibre-rich products.  We can choose:

  • The super fibres: sugarbeet pulp and soya pulp, so called due to their very easily fermentable fibre. Compared with hay, they contain more Hemicellulose and pectins, which are rapidly fermented by micro-organisms, to produce butyric acid.  This is an excellent source of energy for the coloncytes, cells found in the large intestine.  200-400g - dry weight - of the pulps - which must first be soaked thoroughly in water- can be fed daily, this will give general beneficial support in the long run, and will avoid sudden changes in diet.

polpe di barbabietola


  • Pressed hay products: pelletted, cubed, or chopped hay is an excellent way to add fibre to the horse’s diet.  Ideally, they are prepared just like a mash, adding hot water and allowing them to absorb the water, stirring occasionally, for about an hour. Fibre binds the water, which is then released in the large intestine, and helps to maintain a correct amount of liquid, while the fibre has its own essential function in the gut.


Advice for the preparation of a healthy mash:

A good mash will contain fibre-rich foods, and must be given every day, having initially been introduced gradually to the horse’s diet. So for a 500kg horse we would give

  • 200g dry weight of pulp, plus 800g of pelletted or cubed hay
  • OR 1 kg of chopped or pelleted hay
  • OR 1 kg of a commercially produced feedwhich contains at least 18% fibre

Once we have selected the most viable options for our personal situation, we add around 2 litres of boiling water and let that stand for at least one hour.  Before feeding, add in a few carrots or apples, provided the horse chews well, and 30g of brewer’s yeast.

This should be introduced to the horse very gradually, starting off with 300g and increasing the amount very gradually over several days until we reach the desired full dosage*.  Feeding this every day will provide water, fibre and gut-friendly probiotics.

*All changes to diet should always first be checked out with a qualified equine nutritionist, or your vet.


Other articles by Emanuela Valle:

The horses' stomach and nutrition

The teeth and chewing

Viral Numbers

The Whip