News & Advice

Nitrate poisoning is an uncommon, but potentially devastating occurrence on a farm. It is most common in Autumn months but can occur all year round. Grasses accumulate nitrate within the plant when they are growing rapidly, particularly after a drought. Normal photosynthesis on sunny days removes the nitrate, but on cloudy days the nitrate will accumulate in the plant reaching toxic levels. This most commonly occurs in new grass, particularly annual ryegrass, due to tendency to grow rapidly.

We recently had a case on a farm, where approximately 100 animals were grazing a paddock that had been grazed short previously and was rapidly re-growing. Of the 100 animals, 11 were identified as affected, with 6 dying before the Vet arrived and administered the treatment to the remaining 5 animals.

When a ruminant eats grass high in nitrates, it is absorbed into the blood, where it prevents the red blood cells from carrying oxygen around the body. This results in the animal rapidly deteriorating and dying. Clinical signs include dribbling urine, open mouth breathing, wobbly or staggering while walking and muddy brown membranes. The only treatment for affected animals is intravenous injection with a product called Methylene Blue administered by your Vet which reverses the process. Rapid action is required if you suspect your animals are suffering from nitrate poisoning, as mere minutes can be the difference between life and death.

The Forage can be tested at the Vet clinic to check whether it is safe to feed. High nitrate paddocks can be ensiled, as this reduces the nitrate content of forage, as does allowing plants to age and set seed. In contrast, drying plant material such as hay preserves the toxicity.
If high risk pasture must be fed, ensure animals are already ‘full’ and restrict access to one hour at a time, feed other high energy feeds with the pasture and check animals very regularly.

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