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Grazing cereal crops

Dr Jillian Kelly, Regional Vet

Looking around the district, I think many producers will be grazing cereal crops this year, with both sheep and cattle. Crops are great as the fill feed gaps, allows pastures to recover, provide quick green feed and have higher winter growth rates than most pastures.

The provide reasonable quality, palatable feed - protein varies from 8-16%, energy from 6-10 MJ/kg DM and digestibility is 65% or better.

If choosing to graze cereal crops, it is worth considering some animal health issues that can occur.

Calcium deficiency is most likely to affect growing stock (as they have a high calcium demand in their growing bones) and lactating stock (as they are pumping calcium into milk), although it can affect all classes of stock. 

Calcium is important for nerve function, muscle contraction, blood clotting, activation of a number of enzymes and bone formation. Cereal crops (as well as cereal grains) are low in Calcium relative to Phosphorus.

Clinical signs of calcium deficiency include sudden death, muscle tremors, weakness/lethargy and broken bones.

Magnesium is an enzyme cofactor involved in metabolism of carbohydrates, lipids & protein. It has a role in rumen contractility, nerve conduction and muscle contraction. A deficiency is known as "grass tetany" and symptoms include excitability, convulsions, tetany and death. We mainly see this in cattle grazing cereal crops at this time of year.

The high potassium found in cereal crops (and other lush pastures) can inhibit Calcium and Magnesium uptake, making deficiencies in these minerals even more likely on a cereal crop.

Pulpy kidney is also an animal health condition encountered when grazing cereal crops, as like other winter pastures they can be high in water soluble carbohydrates which causes an overgrowth of Clostridal bacteria in the gut and the subsequent death of the animal.

Other issues that can crop up infrequently are nitrate poisoning, acidosis, and awned cereal varieties may cause gum and rumen abscess.

Generally if grazing cereal crops it is important to supplement stock with a source of calcium, salt and magnesium continually while grazing and to vaccinate for pulpy kidney prior to putting the stock out on the crop.

If the crop is really lush and the water content is high, feeding poor quality hay can help to stop scouring, slow down the rumen and improve digestion.

For further information on how to manage animal health issues while grazing crops in your individual situation, or if you have dead or sick stock, please contact your District Veterinarian.