Nia Cooke DEP MEPA(UK)
Alistair Taylor DEP MEPA(UK)



It has been understood for time immemorial that the health of the soil determines the health of those who are fed by its fruit.

We all know that things on planet earth are changing very rapidly, and this obviously affects our horses. Mineral levels in the soil are at a totally different and less diverse mix than they were 100 years ago.  For example, looking at human food (which is researched far more than horse feed!), In an average 100g roast turkey in 1940 you would find, 3.8mg of iron, by 1991 that had decreased to 0.9mg, by 2002 it was down to 0.8mg. 100g of Cheddar cheese in 1940 contained 46.9mg of magnesium, by 1991 it was down to 25, and had perked up a bit by 2002 to 29.(1.)

In 1992, the official report of the Rio Earth Summit concluded “there is deep concern over continuing major declines in the mineral values in farm and range soils throughout the world”. This statement was based on data showing that over the last 100 years, average mineral levels in agricultural soils had fallen worldwide – by 72 per cent in Europe, 76 per cent in Asia and 85 per cent in North America.

Since the 1940's we've lost 90% of our meadow land in the UK, so not only are we losing mineral diversity, we're losing plant diversity.

Some of the earliest cancer research focussed on soil nutrients and toxicities as carcinogenic influences. We've known since medieval times that lack of fruit and vegetables cause scurvy. Lack of vitamin D causes rickets, lack of B12 causes pernicious anaemia - there is a general understanding that vitamin and minerals are essential to all life.

Ecosystems are critical in recycling and redistribution nutrients - consumed by animals and plants and then returned to the soil through wastes deposits and eventual decomposition. Traditional farming techniques maintained soil fertility, through leaving land to lie fallow and rotating crops. Food was consumed close to where it was grown, human and animal manure was spread back onto the fields, even until the middle of the 20th century. But in the last half a century, things are changing rapidly, with a fraction of the organic matter returning to the soil, but with an ever increasing population to feed. This means an ever decreasing level of natural nutrients in the soil, needing more supplemented in the diet, meaning more mined, so we are in a catch 22!

From the WHO "When recycled appropriately, human waste can be a useful resource that promotes soil fertility. However, where waste contains persistent chemicals such as organochlorines or heavy metals, recycling can lead to the accumulation of these pollutants and increased human exposures through food and water. In poor countries, nearly all sewage and most industrial wastes are dumped untreated into surface water. It is uncertain whether the waste detoxification capabilities of the planet as a whole are increasing, decreasing, or reaching a critical threshold at which such services may no longer function effectively".  So perhaps muck spreading human waste isn't the answer either!!

Nitrates are also a very serious issue, a build-up of soil nitrates reduces the biodiversity of plant species by fertilising the faster growing species at the expense of the slower growing varieties. High levels of nitrogen can also cause magnesium, calcium and eventually aluminium leeching form the soil.


Obviously, horses need a variety of vitamins and minerals, and in days gone by they probably would have gotten everything they need from the pasture and hay. The increase in horse disease over the last 80 years suggests that things in their pasture has indeed changed a lot.

So, this all makes feeding the horse a very tricky proposition indeed. There are tonnes of feed balancers and supplements out there, and knowing that the soil is likely imbalanced for our horses nutrient requirements, it's understandable to try and balance your horses diet, but care is needed. For example, we know that UK soil is pretty deficient in Magnesium, and it is not toxic in excessive amounts, so that's a safe supplement. But, horses have a very low nutrient requirement for Vitamin A, which can have a a toxic affect in high levels, so supplementing more Vitamin A, when the horse may already have more than enough from pasture, feed and carrots etc., may well create a negative effect. If you feed your horse lipids, such as copra meal or linseed, the horse needs enough anti-oxidants to combat the oxygenating effect they have on the horses body. All horses would probably benefit from more sodium, given that potassium is high in UK soil. But the above information might just show that we have no idea at what levels of which nutrients each individual field will contain, being as such major changes are happening to our soil.

The only way to know for certain which minerals your horse needs, is to get your pasture tested. If you feed hay, you need to test that too. Or if your vet has diagnosed a deficiency by blood tests. Anything else is just guess work. I'm not saying don't ever feed a supplement or balancer, but be pretty certain why you're feeding it. Too much of certain vitamins and minerals can as much of a problem as deficiencies. There are many companies now who specialise in testing and balancing forage, it is well worth looking at these before you spend money on off-the-shelf solutions, which may well work for some, but which may be adding nutrients that your horse already has problematic levels of, such as iron.


1. THE MINERAL DEPLETION OF FOODS AVAILABLE TO US AS A NATION (1940–2002) – A Review of the 6th Edition of McCance and Widdowson* Dietary

2. WHO: Ecosystems and Human Well-being: Health Synthesis

3. AACR -


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