Diets for horses with PSSM (USA)

At EquiFeast we like to keep things as simple as possible and when we look at some of the diets people have created for PSSM horses our jaws drop. It rather seems that people have been encouraged to try every supplement under the sun. And sometimes the “More must be better rule” seems to be applied. In our view this can create more problems than it serves.

So let’s look at our system and why we use certain things and why we avoid other things.

LAM Essentials (Starter version for a month then follow on version)

This product is a feed balancer (vitamins, minerals and amino acids) plus psyllium (for better insulin/glucose regulation). Most importantly it contains our patented chelated calcium which seems to help a cellular process called Calcium Signalling (CS). This is the way we switch almost every cell on and off. Trials showed it helping horses with EMS, IR and Cushings (actually re-establishing dopamine release in many). Early feedback on PSSM horses is very positive too in most of them across the different variants (click for more detail).

What LAM Essentials doesn’t contain is also important.

  • No magnesium as that is a sedative that blocks the CS process all over the body. It often makes behaviour worse (increasing anxiety and spookiness). In muscles it prevents proper contraction – which may give the appearance of relaxation but isn’t the same as helping the muscle fibres both contract and relax properly (which is what chelated calcium seems to do). The science on magnesium in horses is really clear and consistent but much of the feed industry is in denial about it. Click here for the science.

  • No GABA Agonist herbs or amino acids. These are a group of ingredients (often used to improve palatability) that hit the same receptor in the brain and elsewhere as diazepam (Valium). Again this brain impairment often increases anxiety. Click here for more information.

  • Tyrosine – we use tyrosine in most of our chelated calcium products. But humans with diabetes seems to respond poorly to it and so do horses with IR and EMS. We really have no experience of tyrosine in PSSM horses so for now we leave it out. We often use tyrosine as part of our behaviour “fine tuning” so I expect we will gain some experience in PSSM horses over the next few years. One of our trial horses is about to be given some (late Apr 2021). Click here for more about tyrosine.

Fibre and forage

The simple concept behind EquiFeast diets is that they should be high in fibre and low in starch and sugar. So we encourage people to feed appropriately.

Our primary objective is to turn your pasture and grass hays into good horse feed. So unless your horse has a problem with these feeds, they will make the foundation of the diet. Hay rich in ryegrass, clover and even Lucerne are fine if your pasture is made of native grasses or meadow grasses. Even oxalate pastures will be fine so long as they are not too rich and fast growing. But if your paddocks are rich and growing fast you may need to be sourcing some low carbohydrate, high fibre hay to dilute it with. Or some of the “super fibre” options below.

Hays from grasses like Timothy, Rhodes and “meadow hay” are probably the safest you can get. Good native grasses are also excellent.

Lucerne is a hay that people either love or hate. Generally it is intensively produced so can be very high protein and potassium. For most horses it is fine as a supplementary feed where the pasture is not too rich.

Oaten Hay will normally have a lot of the oat grain left on it. That makes it higher in starch. But oats have been a traditional feed for horses for centuries and there is evidence that, compared to other cereal grains, it is much safer and indeed may have some physiological benefits.

For more concentrated fibre sources consider beet pulp, which is now being imported from the UK, and Copra (from Coolstance in Australia). Both contain what are becoming known as “super fibres” which are more digestible than grass fibre but also appear to boost the digestibility of the fibre in pasture and hay. So they provide a double whammy. A few people report their horses going a bit loopy on copra so test it out gently. UPDATE FEBRUARY 2021 - There is some anecdotal evidence that the relatively high level of oxalate that some beet pulp products contain is contra-indicated if pastures or hay are also high in oxalates. We have a feeling that there are going to be more oxalate pastures in America than is generally thought. Look in particular for kikuyu - even quite well north.

Sunflower seeds are also high in slow release energy as well as protein and make excellent components of the diet. Balancing the omega 3 and omega 6 oils with some micronized linseed is a good idea.

Another protein boosting option is from pulses. I’m not a great fan of soya (quite starchy and too many phyto-estrogens) but lupins claim to have a much better non-starch energy component. Again it is wise to test out how your horse responds to lupins.

Rice bran is another option becoming more available.

The feeds above offer a broad range of fibre, energy and protein options enabling horse owners to adjust their diet whether their objective is to build condition or muscle or just provide energy and protein to maintain horses for work.

They also provide plenty of low starch, high fibre options to help manage horses with EMS, PSSM, Cushing’s or at risk of laminitis, ulcers, colic etc.


Other supplements for PSSM

Every horse is unique and so there is no "one size fits all diet". At EquiFeast we have developed a number of tools to "Fine Tune". We hold you hand during this process and give you the best advice we can.

Unless the horse is on a very oily diet or suffering a lot of muscle break down I doubt there is need for any more anti-oxidants than LAM Essentials provides. Of course these conditions will apply to some PSSM horses. Currently EquiFeast doesn't have products like this in USA however as our PSSM trials progress new products are being developed. Too much vitamin E can be a problem so beware assuming that more is better.

There may be a role for further support to repair damaged tissue and inflammation that results from muscle damage. Our Fight Back product has an enviable record in this area and may benefit a few chronically affected horses. Again our ongoing customer feedback monitoring will help us improve our understanding and we are evaluating a new product that incorporates this powerful approach.

I can see a role in digestive support and our DIGEST supplement is designed for this purpose too. More to study and record.

If horses have a memory of stress we sometimes use tyrosine and tryptophan and these are a part of our behaviour armoury. See note earlier in this article about tyrosine.

Older horses or those capable of harder work despite their condition may benefit from our WINNINGEDGE balancer (BREAK FREE Elite for oxalates) due to its joint and soft tissue support.



Formulating a diet using a variety of different “straights” supplemented with a balancer (like EquiFeast’s LAM Essentials) will provide all the options you need to formulate a feeding routine suitable for your horse.

Click below for our article describing our philosophy and the options in more detail. This article lists some suppliers of feeds with no added magnesium which you may find helpful:

Creating Horse Diets with no Added Magnesium.

Remember that the basic diet proposals we are putting forward here are the same as we suggest for all horses not just PSSM horses. Americans may find them extreme but the trend to high fibre and low starch is probably ten years ahead in the UK compared to the USA. These diets will become more and more normal in the next few years. Just remember that most of the formulated feeds the American industry produces still have magnesium added - you really don't want that.