Warning:

‍A dry autumn significantly increases the risk of lethal nitrate poisoning outbreaks. Spikes in nitrate levels often occur in seasons like the one we are experiencing when seasonal conditions combine in the autumn and winter, particularly following summers and autumns that are drier than normal as rapid uptake of nitrate from the soil by plants occurs with rains following drought conditions. Nitrate levels then build up in pasture when nitrate is taken up by the plant faster than it can be converted into protein.

This can be due to deficiency in plant energy due to plant stress or low sunlight levels, especially in annual grasses and crops with a high nitrate demand. Nitrates can be absorbed quickly by plants when temperatures are low, but conversion to protein occurs very slowly during cold weather causing nitrates to accumulate. The nitrate converts to nitrite in the rumen and then binds to haemoglobin in the blood stopping it from carrying oxygen. Death can occur rapidly due to lack of oxygen to the brain.

Signs of poisoning include muscle tremors staggering and collapse but animals are often found dead. Mucus membranes and teats have a distinctive bluish chocolate colour and blood looks like dairy milk chocolate.

Surviving animals will often abort due to lack of oxygen to the foetus. To reduce the risk of poisoning cattle should not go onto newly sown pasture hungry and should have been fed something high in fibre e.g. hay or silage prior to grazing Introduce stock to high risk paddocks in the early afternoon so that plants have had the sunlight necessary to convert excess nitrate to protein. Warm, dull and overcast days will be more dangerous.

Do not leave on risky pasture overnight. Restrict grazing time to around 1 hour and control the area they have access to. Give time to adjust to the feed by gradually increasing the intake. (This gives time for the rumen microflora to adjust). Check cattle regularly for signs of poisoning. It usually takes 4-5 hours for signs to develop.

To ensure your herbage is safe can test your herbage with a nitrate test kit available from your clinic or we can test it for you. We can help by treating affected cattle with methylene blue, so if you are suspicious of nitrate poisoning or have down cows or young stock after grazing new pasture please call us immediately as time will be of the essence!

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