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two horses with classic PSSM 'look'

Our observation is that horses exhibiting these same symptoms (and more) also can be found ANYWHERE THAT GREEN GRASS GROWS and the horse is not being managed in such a way as to prevent the grass causing issues for that horse. In some cases where green grass isn’t part of the horse’s diet, the hay needs to be checked/analysed.

Compare the list below which is from the following link:
 with the

CHH ‘Health CheckList’. 

There are far too many similarities for this to be merely co-incidence.

- overall stiffness

- the horse appears lazy or can’t move out

- intermittent and/or shifting lameness

- tense belly

- the horse resents being groomed, saddled or cinched up

- the horse seems difficult to train and may display unwanted behaviours such as bucking, rearing or balking

- muscle spasms that can occur all over the horse’s body but are most often seen on the flanks, neck and shoulders

- the horse is unable to move and stretches out as if having to urinate

- general signs of pain

- excessive sweating

- hard muscles, especially of the hind quarters

- pawing the ground

- feeling the need to roll immediately after exercise

- frequently rubbing the body and especially the hindquarters on solid objects or leaning on them with the hindquarters

- difficulty standing for the farrier

- resting with their legs under their body (like an elephant on a circus pedestal) or parked out

- nervous behaviour with a tendency to excessive spooking

- coffee coloured urine during serious episodes

- recumbency during particularly heavy episodes

-difficulty bending through their body, achieving collection under saddle, backing up, lunging and loping

-many PSSM horses go through phases of being more or less or non-symptomatic, which makes them appear unaffected during non-symptomatic periods

Comparing the two lists we found:

· Like ‘grass-affected’ horses there is a wide variety of ‘symptoms’.

· In some horses they ‘come and go’ while in others they can be chronic, acute and even life-threatening. Exacerbation of ‘symptoms’ invariably correlates with the season, weather, changing to a ‘fresh’ paddock/field.

· Like ‘grass-affected’ horses the vast majority respond very well to changes in management around diet and exercise.

· Just as for ‘grass-affected’ horses there is no ‘one size fits all’ answer.

· Just as for ‘grass-affected’ horses there are a lot of assumptions made which result in the unfortunate horse being pts (has ‘neurological’ problems, must have a ‘brain tumour’, their dam or sire had the same ‘symptoms’, having more than one horse from the same family exhibit similar ‘symptoms’)

As with ‘grass-affected’ horses there are basic diet and management principles which broadly work for the vast majority of horses, while there is always a percentage with additional complications that require adjustments to strategy/diet to better fit the individual

 Horses are a fundamentally ‘arid’ environment species. They are designed to live on grass but where the appearance of GREEN (actively growing) grass is only sporadic due to lack of rain.

Hence the equine species has not been exposed to short or lush, certainly not fertilised, green grass ALL YEAR ROUND until comparatively recent times so their genetics have not had time (millions of years) to adapt to the forage and feeds we now impose on them.

It is really not surprising so many of us have ‘grass-affected’ horses!

‘Grass-affected’ or ‘PSSM’

 is there a difference?

When you compare lists of symptoms there is very little difference, it is easy to see why people ask.


Polysaccharide storage myopathy (PSSM) is a disease that results in an abnormal accumulation of glycogen (sugar) in the muscles.

The classic symptoms of PSSM include a reluctance to move, stiffness, sweating, and muscle tremors, and a propensity for “tying-up”.

There are two types of PSSM.

Type 1 is caused by a known genetic mutation and a DNA test is available. Type 2 is also thought to be genetic, but a muscle biopsy can be used for diagnoses.

It is generally accepted that because it is genetic, it is set in concrete however; 


(the science of EPIGENETICS)

The ever expanding list of symptoms for PSSM2 is, ironically, identical to our list for Grass Affected horses.

The recent increase in genetic testing is identifying more and more 'variants'; either all our Grass affected horses (should they be tested) would identify as a variant of PSSM, or could it be that these genes are simply normal in the horse population and the inappropriate environment is causing the expression of these genes?

We have been successfully reversing the symptoms of Grass Affected horses through changes to their diet and environment for over 15 years without any knowledge or understanding of PSSM.

The main difference between the two is that some PSSM horses (known as Type 1) have a genetic mutation which predisposes them to 'tying up' whereas ‘grass-affected’ horses rarely actually ‘tie up’.

Some race-horses and endurance horses do, but not because they have the PSSM1 genes.

‘Grass-affected horses certainly become stiff, hard and tight in their muscles, have difficulty with cantering, bunny-hop and disunite and we have assisted people whose horses have come down with ‘grass tetany’ like cattle do.

By far the most troublesome aspect of pasture grass are the mineral imbalances it can cause. It is the minerals, particularly the electrolytes, which govern the operation of nerves and muscles, influence hormone activity and are inextricably involved with the metabolism of sugars and starches. Any disturbance to their precise ratios plays havoc with the equine metabolism (like dominoes!)

With a more in depth understanding of pasture grass, its stages of growth and how it impacts the horse’s metabolism, people will be able to make more informed decisions resulting in a better outcome for a lot of these horses whether they have been diagnosed with any variant of PSSM or not.

Well on his way to becoming laminitic
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