The good news is that, with the help of the right supplements, you can live with a certain amount of oxalate grass.
On the other hand, you can’t live with Perennial Rye Grass and clover, no matter what you shovel into the horse!
Oxalates are chemicals that are more abundant in warm-season grasses. They latch onto calcium, making the calcium unavailable for the grazing animal to utilise.
It doesn’t take long for the resulting low blood calcium levels to cause the parathyroid gland to produce parathyroid hormone. This hormone tells the bones to release calcium into the bloodstream to make up the shortfall.
You see, calcium is vital to keep the heart beating. For obvious reasons, this takes priority over maintaining strong bones.
If this process continues over a period of time, and more calcium leaves the bones than is deposited back into them, a weak, porous skeleton results. The trouble is, you don’t see this ‘demineralisation’ happening from the outside.
Horses exposed to oxalate pastures can start exhibiting signs of calcium deficiency within a couple of months of being moved onto high-oxalate grasses. However, it’s usually more insidious, with the first signs being vague and non-specific, such as loss of weight and muscle tone and deterioration of coat and hoof quality.
Oxalate Grass Species
Common oxalate grass species include:
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Kikuyu
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Setaria
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Panic
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Guinea
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Buffel
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Pangola
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Signal
Buffel is a warm-season oxalate grass.
Factors Affecting Oxalate Content
Several factors can increase the oxalate content of pasture, including:
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Wet, warm weather and the resulting growth spurts
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Keeping the grass vegetative by slashing
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Fertilisation with nitrogen, phosphates and/or potash, such as NPK fertilisers
Signs of Calcium Deficiency
Signs can include:
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Ill-thrift, loss of top-line and poor hoof quality
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Unevenness of movement or ‘shifting lameness’
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Hard, bony lumps and splints, with a propensity for ‘shin soreness’
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Increased susceptibility to fractures under stress
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X-rays showing demineralisation of bone mass, including the pedal bone in the hoof
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Poor tooth quality, loose teeth and difficulty chewing
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Onset of a ‘dippy’ or sway-back appearance, osteoporosis and arthritis
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Premature end to useful life
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‘Big Head’, where calcium withdrawal from the skeleton has progressed to the point that the bone matrix has been replaced with softer connective tissue, starting with the bones of the skull. Swelling of the jaws and nasal bones can grossly deform the head.
NB: It’s significant that many of these symptoms are identical to those associated with a lack of sodium. It’s likely that the low levels of sodium also found in these oxalate grasses contribute significantly to the calcium deficiency.
Pregnant Mares and Growing Horses
The consequences of consuming oxalate pastures in the adult horse are bad enough, but think about the implications for the pregnant mare and the foal as it grows.
It’s a no-brainer to take steps to avoid calcium deficiency in the growing horse to ensure they’re strong, robust and able to reach their full height without debilitating developmental orthopaedic disease (DOD), including malformations of cartilage, joints and the skeleton.
Managing Calcium Availability
Prevention is far easier and cheaper than ‘cure’.
It can take up to 12 months of correct supplementation to re-mineralise bones, during which time the horse should not be ridden to avoid possible fractures.
The primary principle of prevention is not just to supplement heaps of calcium — calcium is useless on its own.
Equally important are the ‘co-factors’ or other nutrients essential for calcium to be absorbed across the intestinal wall and into the bloodstream, where it’s available to carry out its many functions, one of which is becoming part of the bone structure.
The primary principle of prevention is to ensure calcium does not leave the bones!
This requires the presence of not only calcium but also the various co-factors, which include:
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Magnesium
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Boron
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Phosphorous
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Sodium
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Vitamin D
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An acidic environment
Chelated calcium is already bound to an amino acid and therefore can’t be ‘stolen’ by oxalates.
An excellent supplement will contain chelated calcium plus the co-factors mentioned above. Feeding the right sort of calcium alongside your multi-vitamin and mineral supplement, which contains the necessary trace minerals and essential vitamins, will help keep your horse strong and healthy and greatly extend their useful life.
What’s Wrong with Calcium Carbonate or DCP?
1. You have to feed large quantities
Because calcium carbonate is inorganic, you have to feed large quantities — up to 200 g per day for a 500 kg horse. The more you feed, the less absorption is achieved.
2. It can affect the gut environment
Calcium carbonate tends to alkalise the gut environment, which is counterproductive to calcium absorption.
3. The essential co-factors are missing
Calcium carbonate and DCP don’t provide the essential co-factors required for calcium utilisation, particularly Vitamin D, magnesium and boron.
Vitamin D is needed for calcium to move from the intestine into the bloodstream. Magnesium is needed for calcium to be deposited into the bones, while boron helps reduce the loss of calcium and magnesium through the urine.
What About Lucerne (Alfalfa)?
Sure, lucerne is high in calcium, but it’s also low in phosphorous. It’s very high in potassium and very low in sodium.
It’s another unbalanced feed that has to be compensated for.
If your horse already has an imbalance from the grass, feeding lucerne can simply add more complications.
Instead, feed plain grass hay — Rhodes is ideal — with the appropriate Calm Healthy Horses supplements, including Supreme MVA and XtraCal.
Real Results: Big Head Recovery
See our Horse Testimonials page to read about a horse that recovered from ‘Big Head’ using Calm Healthy Horses supplements.
The Big Head Disease Recovery testimonial tells the story of a horse diagnosed with nutritional secondary hyperparathyroidism and the subsequent recovery following nutritional support.
For more advice, complete our complimentary Horse Questionnaire.