At this time of year, farmers need reminding of the risks of nitrate poisoning in greenfeed crops.
The sudden deaths that can occur due to high nitrates in greenfeed crops, can be devastating and cause large economic losses.
While testing is important, many crops after a drought has broken will be high in nitrates and careful management is needed if these crops are to be grazed.
Often after a drought farmers have little other feed avaliable, and if greenfeed crops are used seek advice how to manage this situation so losses are avoided.
Several cases of nitrate poisoning in livestock have prompted a warning from Oamaru veterinarians that recent rapid growth of winter crops has also elevated nitrate levels, reports The Otago Daily Times.
Oamaru Veterinary Services vet Kevin Kearney said in one case seven rising yearling heifers strip grazing short rotation rye grass were found dead, while tests on other winter crops in the region also revealed elevated nitrate levels.
Mr Kearney said nitrates accumulated in plants during periods of rapid growth, especially after rain following extended dry periods, as had happened this autumn.
They could also accumulate in plants during flowering or regrowth, in overcast, dull conditions, frosty weather and when there was leaf damage from hail, herbicides or plant disease. Death from nitrate poisoning was rapid with animals suffering from a lack of oxygen.
Mr Kearney recommended introducing animals to winter crops slowly and not when they were hungry, suggesting they first be fed hay, silage or baleage.
He also suggested only half an animal's daily intake come from brassicas and, after a frost, farmers should let the crop thaw before letting stock have access.
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