Springing! – Major Diet Changes 18

In humans, the use of acid-suppressing ulcer treatments has been linked to osteoporotic fractures. In a study of 5755 men, anti-ulcer treatment was associated with an increased risk of fractures, but only among individuals not taking calcium supplements. In horses, there is concern as to whether omeprazole use may be a risk factor for skeletal injury in performance horses. A balanced diet, supplemented with the correct minerals and the right amino acid profile, is especially important for any horse on anti-ulcer medication. Lucerne is also good to include as it has demonstrated buffering and anti-ulcer capacity. There is a strong correlation between horses fed lucerne hay and a lower degree of gastric ulceration.

• Diet, minerals and spring subtropical pastures – soluble AND insoluble oxalates cause problems for horses - Many subtropical grasses such as kikuyu, setaria, buffel and panic bind minerals to oxalates as part of their normal growth. Most plants species contain oxalates, but at low levels. Some mineral-oxalate combinations such as potassium and magnesium oxalate are soluble – ie they dissolve in the horses stomach, releasing the potassium and magnesium and oxalate. The horse can then absorb the potassium and magnesium. Calcium oxalate is not soluble ie it doesn’t dissolve in the horses gut and the horse doesn’t get the calcium. This means the diet is calcium deficient

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and blood calcium levels fall. Calcium is crucial to many body systems, and blood levels are tightly regulated – if they fall, the body moves calcium from the reservoirs in the bones to ensure blood levels are maintained. The body will sacrifice bone strength to maintain calcium levels in the blood and if this continues for a few months, the bones lose mineral density.

Loss of bone density = osteoporosis and it can be mild or severe. Osteoporosis (also known as nutritional secondary hyperparathyroidism (NSH)) was called ‘bighead’ when it was first recognised in the 5th century. However, less than 20% of affected horses develop a big head and there are in fact, three classical clinical manifestations: illthrift, lameness, and swelling of the maxilla and mandible. Most cases of NSH in Australia occur in spring, summer and autumn – after grazing oxalate pasture is 2-8 months. Grass oxalate levels are highest in early summer and lowest in late autumn. As spring transitions into summer, particular attention needs to be paid to mineral intakes – especially calcium.

And, it’s not just insoluble calcium oxalate that causes problems for horses - soluble oxalates can bind to any calcium in the diet and they can also be absorbed. Some plants such as setaria have up to 70g of soluble oxalates per kg – so a horse eating 10kg of grass a day will also be consuming 700g of soluble oxalates every day. Over time this generally leads to kidney disease as the oxalates form crystals in the kidneys. This occurs in humans and other animals too. In humans, milk and inorganic calcium such as lime are used for soluble oxalate ingestion. In horses grazing oxalate-containing grasses, calcium supplementation must include both organic and inorganic forms of calcium when soluble and insoluble oxalates are part of the diet.

The diets of many horses are borderline in calcium or are low in calcium and high in phosphorus – not only horses on oxalate pastures, but even normal pastures, diets and feedstuffs. As in humans, we often don’t recognise the early signs of osteoporosis – not until a fracture occurs. Be sure to check your horses intake of minerals and calcium, especially in spring and when they on acid-suppressing treatment for ulcers or if they are pregnant, lactating, growing or working.

All content provided in this article is for general use and information only and does not constitute advice or a veterinary opinion. It is not intended as specific medical advice or opinion and should not be relied on in place of consultation with your equine veterinarian.

ABOUT THE AUTHOR –Dr Jennifer Stewart

CEO BVSc BSc PhD Dip BEP Equine Veterinarian and Consultant Nutritionist Dr Jen Stewart has been an equine veterinarian for more than 40 years and an equine nutritionist for more than 10 years. Jen has been developing premium formulas for studs, trainers and feed companies in Australia and around the world and regularly consults to leading international studs and trainers in various countries. Jen has spent a fair bit of time researching and being involved in nutritional management of developmental orthopaedic diseases, colic, tying-up, laminitis, performance problems, post-surgery and other conditions. And is currently the only practicing equine veterinarian and clinical nutritionist in Australia. Jen’s promise is to continue to BRING SCIENCE TO YOUR FEED BIN

www.jenquine.com