TWO types of oxalates = 2 serious veterinary clinical problems for horses
SOLUBLE and INSOLUBLE OXALATES……the reason we need to feed inorganic AND organic calcium.
There are 2 types of oxalates: ones that are soluble and dissolve in the horse’s gut + ones that are insoluble and don’t dissolve. Grasses like kikuyu, panic, setaria, buffel and other sub-tropical species contain oxalates. The oxalates in the plant are bound to minerals including sodium, potassium, magnesium and calcium. Sodium, potassium and magnesium oxalates are soluble and the minerals can be absorbed by the horse. Calcium-oxalate is insoluble and can’t be absorbed.
SOLUBLE OXALATES When the horse eats the grass, the sodium, potassium and magnesium oxalates (but not the calcium oxalate) dissolve in the horse’s stomach releasing the sodium, potassium, magnesium and oxalate. The horse can then absorb the free sodium, potassium, magnesium and oxalate into the blood. The horse uses the sodium, potassium and magnesium - but it has no use for the oxalate. However once absorbed into the blood, the soluble oxalates will bind to the blood calcium. Both the free oxalate and the calcium oxalate in the blood are transported to the kidneys for excretion in the urine.
Once in the kidneys, the oxalate forms crystals and stones that damage the kidney and cause renal failure. Just recently we’ve seen 2 cases – an aged gelding and a 2yo stock horse x quarter horse that died due to fatal kidney damage caused by oxalate crystals accumulating in the kidney. The kidney damage showed up in blood tests and on ultrasound examination, and (sadly for all) were confirmed by micro-scopic post-mortem examination (histopathology) of the kidneys.
Soluble oxalates have a high affinity for calcium. When in the gut, an inorganic form of calcium helps prevent absorption of soluble oxalates. Inorganic forms of calcium that can prevent oxalate poisoning include di- and mono-calcium phosphate and calcium carbonate. Jenquine Bone Formula Forte and Calsorb Forte provide inorganic forms of calcium to reduce the risk of soluble oxalate absorption and kidney damage.
INSOLUBLE OXALATES Calcium-oxalate in the grass is insoluble in the horses gut. Because the calcium-oxalate cannot be dissolved to release the calcium, the diet can be calcium deficient. Providing an already chelated form of organic, absorbable calcium prevents the free soluble plant oxalates from binding to the calcium in the diet. Jenquine Bone Formula Forte and Calsorb Forte include organic, chelated calcium.
Dr Jennifer Stewart
Equine Clinical Nutrition
