Incidents of poisoning in grazing stock have been associated with the application of fertilisers and conditioners on to grassland in dry conditions. Although cases are uncommon, the cases seen are usually avoidable.
The products implicated vary in type and include nitrogen based fertilisers which have caused nitrate/nitrite toxicity and recently selenium supplemented fertilisers which have caused selenium toxicity.
In two recent incidents of selenium toxicity investigated by AHVLA, poisoning has been as a result of sheep having access to treated pastures when the fertiliser was still visible on the ground. This was primarily due to a lack of rain which would normally dissolve and allow the chemicals to soak into the ground.
Both ewes and lambs were affected and were found dead or died quickly after being found recumbent. Occasionally animals may show difficulty breathing prior to death. Because of the rapid onset of clinical signs, treatment is often unsuccessful. Post-mortem examination of affected lambs from the two farms showed typical changes including fluid filled lungs and fluid in the body cavities.
In other instances stock have had access to nitrate fertiliser spilled on pasture or have broken into storage areas. Spillage may occur in areas of fields where spreaders turn or are loaded. Cattle are more susceptible to nitrate poisoning than sheep. Clinical signs include difficulty breathing, muscle tremors, diarrhoea, recumbency and death if a fatal dose is consumed. Cattle may abort a few days after exposure. Treatment of affected animals should be discussed with your vet surgeon.
We advise that, prior to moving stock back to treated pastures, farmers carefully check any fertiliser applied is not readily visible.
We also continue to be alerted to incidents of botulism in sheep and cattle associated with spreading of broiler litter on to grazing land. The clinical signs vary from sudden deaths, to animals becoming stiff, wobbly and going down before dying. Some cases have slowly become weaker and unable to eat or drink necessitating euthanasia on welfare grounds. We do not advocate the use of broiler litter on grazing land, advising that its use is limited to fields that are to be deep ploughed directly after application.
There are undoubted benefits of applying fertiliser to improve growth and quality of grass. By carrying out a few simple checks, fertiliser application can be carried out safely and effectively, while protecting the health and welfare of your stock.
1. Follow any specific manufacturer’s or supplier’s instructions when applying fertiliser.
2. Note that some products stipulate animals should not graze pasture until light rain has washed the product off the "leaf".
3. Remove any spillages from pasture ensuring livestock do not have access.
4. Ensure livestock do not have access to areas where fertiliser is stored.
5. Do not use broiler litter on grazing land. Preferably, litter should be deep ploughed directly after application.