With the arrival of rain, high-oxalate grasses flourish, posing a risk to your horse’s calcium levels. Without proper supplementation, prolonged exposure can lead to calcium deficiency, osteoporosis, and serious musculoskeletal issues. Understanding which grasses contain dangerous oxalate levels and how to prevent deficiencies is crucial for maintaining optimal equine health.
What Are High-Oxalate Grasses?
Oxalates are naturally occurring compounds found in many grasses. However, when oxalate levels exceed 0.5% (5g/kg of grass), they can interfere with calcium absorption, leading to deficiencies and severe health issues in horses.
Common High-Oxalate Grasses in Australia:
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Buffel grass (Cenchrus ciliaris) – 1.8% to 6.5% oxalate
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Setaria (pigeon grass) (Setaria sphacelata) – 1.37% to 7.8% oxalate
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Pangola grass (Digitaria eriantha ssp. pentzii) – 0.9% to 1.8% oxalate
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Guinea grass (Panicum maximum) – 0.6% to 2.4% oxalate
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Kikuyu (Pennisetum clandestinum) – 0.8% to 3.4% oxalate
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Para grass (Brachiaria mutica) – 0.85% to 1.68% oxalate
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Signal grass (Brachiaria decumbens) – 0.9% to 1.3% oxalate
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Purple pigeon grass (Setaria incrassata) – 0.67% to 1.9% oxalate
Oxalate levels are highest in young, rapidly growing grass, particularly in Spring and Summer. However, studies in high-rainfall areas of Queensland and NSW indicate that elevated levels can also persist in Autumn and Winter.
The Link Between Oxalates and Calcium Deficiency
Horses require a balanced calcium intake for strong bones, joint function, and overall well-being. When consuming high-oxalate grasses without proper calcium supplementation, horses are at risk of nutritional secondary hyperparathyroidism (NSH), also known as 'bighead disease' or osteodystrophia fibrosa (ODF).
Signs of Calcium Deficiency in Horses:
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Shifting lameness and joint pain
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Shortened stride and reluctance to move forward
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Increased time lying down and general weakness
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Preference to canter instead of trot
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Ligament and tendon injuries
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Weight loss and rough coat
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Spontaneous fractures and splints
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Chewing issues and loose teeth
Importantly, less than 15% of affected horses develop visible ‘bighead’ swelling, making early detection and prevention critical.
How to Prevent Oxalate-Related Calcium Deficiency
Providing adequate daily calcium supplementation is essential when horses graze on high-oxalate pastures. However, not all calcium supplements are created equal.
Key Considerations for Calcium Supplements
A well-balanced calcium supplement should include both inorganic calcium carbonate and organic (chelated) calcium to ensure optimal absorption and prevent oxalate interference. Additionally, essential bone minerals such as phosphorus, magnesium, and vitamin D play a crucial role in enhancing calcium uptake and maintaining bone strength. For long-term use, supplements should also be highly palatable and easy to mix into daily feeds, ensuring consistent intake and effectiveness.
Recommended Calcium Supplements for Horses
At Woonona Petfoods, we offer premium calcium supplements to help prevent deficiencies and support strong, healthy bones. Vetsense Gen Pack Calcium Carbonate is a 100% natural feed-grade calcium powder containing 40% elemental calcium, making it ideal for foals, breeding stock, pregnant mares, stallions, and horses on high-oxalate pastures. For a more comprehensive solution, Kohnke’s Own Cell-Osteo provides a premium blend of calcium, phosphorus, magnesium, and essential vitamins to enhance bone strength and soundness, particularly in young horses and those undergoing intense training. It is also recommended for horses on grain-based or fat-boosted diets where calcium levels may be imbalanced.
High-oxalate grasses are a hidden danger that can severely impact your horse’s health. Preventing calcium deficiency with the right supplementation ensures strong bones, healthy joints, and peak performance. Don’t wait for symptoms to appear, protect your horse today!
