Mineral Imbalances 08/09/2015

Unless you have been organically farming for years, your pasture WILL BE minerally imbalanced. In particular it will be deficient in calcium and possibly magnesium. Rye-grass and clover are inherently very high in potassium and low in sodium, especially under certain climatic conditions frequently encountered in autumn and spring. These macro-minerals are so vital to life that if the animal isn’t getting them from the grass he is eating then we must supply them in the form of a supplement for the following very good reason…

The body pH of the horse (or any mammal including us) is supposed to be 7.365 (slightly alkaline). When the pH drops to less than 7, from eating too much sugar/carbohydrate from grass and molassed grains, the body becomes acidic. Numerous health problems arise from this state of ‘acidosis’. If the diet does not contain enough calcium and magnesium then the body has to continually swipe these vital minerals from the bones, muscles, (including the heart), nerves, and brain, to maintain this ever so slightly alkaline pH.

In layman’s terms, here are some facts. Think about them and draw your own conclusions!!!

Calcium excites the nerves and magnesium relaxes them. The brain is part of the nervous system! (‘Attention Deficit Disorder’ type symptoms).

They ‘lose the ability to process information’ (can’t think straight), you have difficulty getting their attention, they become over-sensitive, spooky and cause accidents and so on.

Calcium is necessary for muscle contraction and magnesium is necessary to release them.

Horses are 80% muscle; lack of calcium/magnesium causes ‘spasticity’ of back muscles, tight hamstrings, tenseness, muscle cramps.

Boron is a ‘synergist’ for calcium and magnesium, which means it helps calcium and magnesium to do their jobs. In the absence of boron, up to 40% of calcium and magnesium is lost in the urine. Boron is also commonly lacking in our soils, more so in regions of high rainfall.

Calcium, magnesium, boron along with copper, are high on the list of minerals necessary for proper bone formation and maintenance as well as joint health.

Spring time (worst time of the year for mineral imbalances) is when mares are in the third trimester of pregnancy, and are nurturing their growing newborn foals (increased requirements).

Lime is calcium, so liming is a good start and will help take care of part of the daily calcium requirement.

Magnesium is not so easily applied via the soil short term.

Our climate in Australia is changeable, warm and wet. The spring and Autumn ‘flushes’ are well known with their associated problems, but there are many slightly lesser ‘flushes’ throughout the year depending on climatic conditions.

Rapidly growing (short) grass which is usually bright lime green, even the tiniest shoots will be full of potassium and NSC (non structural carbohydrates), this mainly occurs in Autumn and spring. Excess NSC can trigger laminitic attacks especially in horses that are prone to laminitis. The surge in potassium will cause a major mineral imbalance, until just recently this has not been recognised at all in horses. It has been well documented in cattle and is called grass tetany or known as ‘grass staggers’ to differentiate it from ‘rye-grass staggers’ caused by the Lolitrem B endophyte in the rye-grass.

Horses with grass tetany will show symptoms very quickly (over night usually) they will suddenly appear very stiff in their hind legs and may even look like they are lame in the back leg(s). Some will even point their back toe like they have a hoof abscess, if left then the next morning you could find them pointing the opposite back leg. Some horses will have trouble getting up from lying down, and some can’t get up. If not treated it could lead to long term effects on the horses movement, in severe cases it can be fatal. Some horses will show mild signs by stepping short with their back legs.

Any grass under stress or climatic conditions such as those of early spring and autumn, especially in drought-breaking rains or cool, cloudy, wet weather, including frosts, is subject to acute spikes of potassium and nitrate at the same time becoming low in sodium. This is exacerbated by nitrogenous fertilisers. The potassium nitrate ingested is highly toxic and the body eliminates it by latching on to calcium and magnesium and is excreted with them. Hence the necessity to feed adequate calcium/magnesium and sodium while not adding to the potassium load with lucerne/molasses, many herbs/garlic/high protein feeds/supplements containing potassium.

There is a huge emphasis in New Zealand on grass production, and comparatively little on the health of the stock that are eating it. Many of the pastures our horses are grazing are primarily for sheep and cattle, and are more suitable for improving weight gain and milk production. Furthermore, they are fertilized with substances that promote rapid growth thereby exacerbating the mineral imbalances.

In Australia it’s not uncommon for large cattle farms to be subdivided up into smaller lifestyle properties which are subsequently used to graze horses.

Magnesium is one of the most important minerals in the cell. Some is stored in the body, mainly in the skeleton, muscles including the smooth muscle of the heart from where it is released when deficiencies occur in the diet. Magnesium plays a vital role in the activation of around 350 enzymatic processes in the body including breakdown of blood glucose. Blood magnesium levels rise after the horse eats glucose or carbohydrates.

Simplified: low magnesium = a reduced insulin response. It therefore contributes significantly to the development of obesity, the ‘diabetic’ horse, associated laminitis and eventually to the “Cushings-like” syndrome.

Spring grass is especially high in glucose and low in minerals including magnesium. Deficiencies affect the cell membranes of nerve and muscle tissue, leading to many of the above symptoms, especially the ‘hypersensitivity’ ones.

Magnesium is one of the essential electrolytes, along with calcium and potassium. Too much calcium and/or not enough magnesium can predispose a horse to ‘tying up’ (severe muscle cramps).

Symptoms include:

  • Excessive spookiness/alertness/excitability
  • Stepping short behind, not tracking up
  • Chronic saddle fitting problems
  • Loss of appetite/poor condition
  • Nervousness
  • Exhaustion
  • Cramps
  • Cardiovascular irregularities
  • Hypersensitivity to noise
  • Grinding the teeth, doesn’t like the bit, unquiet mouth

Magnesium sulphate can be fed short term, however, regular feeding can lead to gastro-intestinal upsets, even diarrhoea. Magnesium oxide is a form of magnesium that is usually applied to the soil. From there it would be processed through the plant into a form that the body can utilize. It is imperative to feed a highly absorbable, organic form that is non-toxic and whatever the horse doesn’t need will go out with the urine or manure.

Magnesium needs to be part of the right feeding regime for your horse, according to his lifestyle.

Kikuyu grass contains oxalates which bind up calcium making it un-absorbable by the horse’s intestine (read Bad Grasses list on this web site for other oxalate grasses in Australia). Horses grazing pastures with significant proportions of kikuyu definitely need to be supplemented with calcium. Feeding some lucerne along with a good calcium supplement is a good option but bear in mind some horses cannot tolerate lucerne because it is high in potassium and fluorescing pigments which can cause photosensitivity. Photosensitivity can appear as a persistent mud fever or sun burn particularly on unpigmented skin of white patches (also see Photo-sensitivity).

Kikuyu grass is not high in nutrition, it is important to have a good feeding regime when kikuyu is prevalent in your pasture.

Calcium is very important particularly when the majority of soils in Australia are generally under half the calcium levels recommended. Calcium is crucial for good gut health in horses, not to mention for all their vital organs. Leg splints can form for no apparent reason and facial crests on growing horses that are not getting enough calcium while grazing Kikuyu. In Queensland and Northern NSW oxalate grasses are a huge problem, there are some warnings about the grass but depending which state or territory you are in the information may be contradictory to an adjoining state and very confusing.

In Queensland and Northern NSW it is commonly known as ‘Big Head’ or ‘Bran Disease’, the technical name is hyperparathyroidism. Common symptoms of ‘Big Head’ are affected gait, poor performance and swelling of bones of the head. Horses grazing oxalate grasses like Setaria or Kikuyu for a period of time that are not being properly supplemented in calcium may experience demineralisation and possibly an enlarged thyroid gland or otherwise known as goitre. The parathyroid gland inside the thyroid releases a hormone which melts the bone to maintain calcium levels in the blood. If calcium levels drop in the blood below normal this could have a detrimental effect on the horse’s survival so their body is designed to maintain the correct calcium levels at all times (this is called homeostasis). That’s why it’s unusual to see low calcium levels in blood tests and if you do see this the horse would be by this time seriously ill.

Kikuyu grass also binds up sodium so it’s important to also feed plain (non iodised) salt. Salt can also act as a buffing agent for acid in the horse’s body, including lactic acid and acidosis of the hind gut. Salt is also vital for the drinking reflux, over autumn / winter if you notice your horse’s manure getting dry this is probably because they are not drinking enough water in the cooler conditions. Increase the salt by 10gms each couple of days until the manure is back to normal, a good starting guide for feeding salt is 10gms per 100 kg of body weight.

Salt and Calcium are the two things that will vary in a horses diet according to the situation they are in, for example heavy work load, extra sweating or in foal. Vitamin and Mineral supplements on the market are designed to add Calcium and Sodium separately for this reason, the only problem with this is they DON’T TELL YOU! Fine non iodised salt is easily available at your local produce store.

It is important to note that for proper calcium absorption other elements such as Magnesium boron and copper must be present. It has also recently been documented that magnesium is also bound up by oxalates, not to the same extent as calcium but it explains why so many horses on oxalate pastures are also showing all the signs of magnesium deficiencies.

Horse people are notorious for thinking that if one scoop is good two must be better. This is not the case with Vitamins and Minerals. There are some minerals such as Selenium that can become toxin if over dosed. Calcium and salt should also not be over dosed, so always stick to the manufacturer’s dose rate or check with your veterinarian.

B-Vitamin Deficiency is Caused by a Lack of Fibre

Within the large intestine of the horse, there should be a healthy population of ‘good’ bacteria, whose purpose it is to breakdown the food further, producing energy-rich, short-chain fatty acids. These bacteria also produce essential B-vitamins of which biotin is one and Vitamin K necessary for just about every function in the body, including healthy red blood cells and optimal function of the nervous system, healthy hair coat and strong hooves.

Signs that a horse is not making sufficient of his own B vitamins are poor appetite, sour attitude, anaemia, poor hooves and skin conditions.

Biotin is one of this large group of vitamins. Everyone is busy supplementing with biotin to improve hooves when all the horse needs is more fibre in his diet so he can make his own. Hooves will not be strong and healthy on a sugar diet!!

Anything that upsets digestion, such as a low roughage diet, (e.g., spring-time sloppy manures caused by acidosis) or increased stress of any kind, will interfere with the horses ability to produce his own B vitamins.

It is a good idea to make sure your multi vitamin/mineral supplement has the full range of B-Vitamins. The range of Vitamin B’s are water soluble and not stored in the body, you cannot overdose on them.


Selenium is essential to good health in the horse. It is a trace mineral which helps to make important antioxidant enzymes that have several functions in the horse’s metabolism. These selenium containing enzymes provide antioxidant protection in every cell of the horse’s body. They also have roles that affect growth, immune function, muscle recovery and reproduction.

Many areas of New Zealand and Australia have soils deficient in selenium, which means unless you are supplementing with it, your horse is likely to be deficient. Too little selenium in the diet is a problem, it’s a bit like trying to run a car without oil, causing degeneration of muscle tissue, stiffness of gait and a predisposition to ‘tying up’. However, too much selenium is a problem as it is toxic to your horse. This has become more of a possibility since selenium is now added to a lot of feeds.

Annual blood tests are essential, so you know exactly how much to supplement with.

It is best fed in small doses often, as in the organic forms available that you add to a daily feed.

by Jenny Paterson B.Sc (New Zealand)

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