Get Grass Smart – Important Points About Potassium
Potassium is in everything your horse consumes. We have come to realise, from the many forage analyses we have conducted that domestic horses are often subject to over-load and the effects on the horse’s metabolism are under-estimated.
Electrolytes are minerals in the blood and other body fluids that carry an electrical charge. Electrolytes affect how your horse’s body functions in many ways, including nerve impulse transmission, muscle function, fluid balances and blood pH.
Many of the issues people experience with their domestic horses are related to excesses of this very important electrolyte (symbol K).
Plants LOVE potassium and uptake more than their actual requirements. Potassium is involved in and inseparable from, water uptake into plants this is one of the main reasons why many horses are 'worse' soon after a rain event.
Hence green, growing grass is always high in potassium and low in sodium.
This places a constant stress on the horse's adrenal glands which have sensors to trigger production of the hormone aldosterone which tells the kidneys to get busy excreting potassium while at the same time conserving sodium – a process horses ARE adapted to EXCEPT, unlike in their natural habitats, in the domestic setting it can be unrelenting.
On analysis, green, cool season grasses are inevitably 2% potassium or higher. High potassium forage strongly correlates with the more serious ‘grass-affected’ issues.
When grass is 2% K and a 500kg horse consumes 10kgs of such grass per day, he is ingesting 200g of potassium. Grass that causes trouble can be 3-4.4% K - meaning the horse consumes 300-440g potassium. Actual daily requirements for a 500kg horse are more like 25g – 40g/day.
This is why, when the horse is already consuming high potassium cool season grasses (NZ, UK and southern states of Australia), he is ALREADY IN OVER-LOAD so it is better not add more with other high K items like lucerne/alfalfa.
In our experience, while the statement “Potassium is easily excreted in the urine” is true, the assumption high potassium ‘is of no concern’ is not correct.
The Nutrient Requirements of Horses (NRC) says that ‘excess potassium is excreted readily’ but in the sister book: ‘Mineral Tolerance of Animals’ it states the ‘safe maximum tolerable levels for non-ruminants (horses) would be 10,000mgs/kg’ which is a mere 1% - a level never seen in short or lush green forage, especially in cool, season grasses and lucerne/alfalfa where it is closer to 2% or more, even more (3-5%) in dairy or rye/clover pastures and even more in fresh herbs like Cleavers/Cow Parsley - toxically high at 7%!
Hay on the other hand, depending on the soils in which it has grown and the stage of growth at which it is harvested, tends to be less than 2%. Exceptions are when there has been fertiliser applied to increase yield.
‘Native’ grasses growing on unimproved soils tend to be lower in K, closer to the desirable 1%.
Generally, the more mature the plant the lower the K content. This is why ‘late cut’ hay works best for horses with more serious issues like head-shaking.
If you are getting hay analysed best to include Minerals which includes K, as well as Sugars. Luckily potassium can be drastically reduced by around 50% in hay with soaking.
The purpose of our CHH recommended diet adjustments is to de-stress the horse’s metabolism – to give it a rest and make it easier for him to balance his own minerals.
This is why we advocate being mindful of potassium intake (eg green grass, legumes like clovers and lucerne/alfalfa, molasses) because it is so easy to inadvertently put horses into ‘overload’ and this can precipitate a cascade of metabolic issues (sometimes catastrophes) which you will see manifesting in symptoms such as spooking, ‘tight muscles’, sacro-iliac, HS, laminitis, digestive and respiratory issues and/or other signs of ‘Grass Affectedness’**.
It is significant that muscle contraction causes potassium to be released from muscle cells into the bloodstream. Not a problem under normal circumstances but a likely reason why many ‘grass-affected’ horses get worse with exercise, especially HS horses.
Being mindful of Potassium intake is very similar to how you manage Nitrogen intake.
Particularly when your horse has ‘issues’ it is essential to:
• Reduce green forage intake by controlling, in some cases eliminating altogether, access to green grass
• Feed more plain grass hay
• Avoid Lucerne/alfalfa/clovers/kelp/molasses
• Be aware that fresh herbs like Cleavers and Cow Parsley are toxically high in potassium (7%)
• Add salt to feed (10gms per 100gm liveweight)
Photos: Axel had been living on short, green clover-riddled over-grazed grass
We did nothing else other than change Axel's diet and lunge him once a week or so to monitor progress.
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