Nitrate poisoning – we can’t be too careful this year

Un-seasonally warm temperatures; humid dull days and explosive plant growth rates have created the ultimate high risk environment for nitrate poisoning on many farms this season.


All types of fast growing, young forage should be regarded as high risk at the moment, not just the usual culprits like annual ryegrass and oats. However, there are some steps that can be taken to reduce the risks in conditions like we are seeing now.   


One of the challenges with nitrate poisoning is that it typically happens very quickly, so by the time farmers see animals showing symptoms in the paddock it can be too late to reverse the situation, although an antidote is available.


Poisoning occurs when the plant’s uptake of nitrogen from the soil exceeds its ability to utilise that N so the surplus gets stored in the leaves. 


The first step in managing the risk is careful monitoring. Farmers can test herbage nitrate levels using testing kits available from the vet or samples can be sent away to get analysed. Either way a quick answer as to the status of the crop is available, often on the same day.


The second step is to be careful with grazing policies. The most important strategy is to never put hungry stock onto a suspect crop or paddock without giving them something else to eat first, like hay, silage or PKE. That way they won’t eat so much of the potentially toxic forage and they will also eat it more slowly.


If it’s a winter crop, feed only low levels initially and build intakes up over 14 days.


Other possible strategies include shifting stock twice a day to reduce their rate of intake. Usually older animals are less susceptible than young ones, but all stock classes have been affected this year.


Regardless of stock age or forage type, avoid grazing too low – nitrate levels are higher in the base of the plant.

They’re also higher in the morning than the afternoon, so avoid grazing problem crops early in the day.

If farmers have been using fast grazing rounds to stay on top of growth rates, it’s important they avoid putting stock onto pasture growth that is less than 21 days old.


Symptoms of poisoning are animals appearing weak and staggering, gasping for breath, and rapid deterioration often leading to death. Abortions can also occur without other symptoms.


Monitor animals carefully and at the first hint of trouble remove stock from the toxic feed source straight away and contact the vet.