Nitrate poisoning, is a relatively common problem in grazing livestock in our temperate climate, and often follows when livestock graze young, rapidly growing pastures and crops that haven’t converted all their nitrates into protein.
The results of nitrate poisoning can be very dramatic, with animals often giving no warning and collapsing suddenly. Accumulation of nitrites in the rumen leads to these being absorbed into the blood stream. The nitrites bind with haemoglobin and thus limits the oxygen carrying capacity of the red blood cells. Animals become oxygen starved and without prompt treatment can die.
Which animals are commonly affected?
Sheep, cattle, deer and goats all get nitrate poisoning. Cattle are the most susceptible, and sheep the most resistant.
What symptoms can I expect to see?
How long does toxicity take to occur?
A cow can consume a toxic amount of nitrate in one hour, and can start to show signs very soon after. If cows are grazing a toxic paddock, then there can very quickly be a number of animals affected and it becomes real emergency. It can take up to four hours for signs to become evident so animals should be monitored closely during this one to four hour period when grazing suspect crops.
What climatic conditions predispose plants to accumulating high levels of Nitrate?
Basically, conditions which cause rapid growth spurts will predispose plants to accumulating high levels of nitrate. It is commonly seen under the following two scenarios:
How do I minimise the risk of nitrate poisoning?
The best advice is to bring any suspected crops in for testing prior to feeding. Samples need to be at least a full bread bag size.
If crop is above 1% nitrate content, then give other food first, especially high energy food, so that rumen bacteria can work at full speed. Graze the crop for 1-2 hours only. Graze in afternoon when the crop has had maximum exposure to sunlight, which decreases the nitrate levels. If results is above 2% don’t feed till retested.