I got a call from a client who had one cow already dead and eight more with varying degrees of nervous signs, ranging from dullness to severe convulsions in the worst-affected animals. Some cows had a profuse diarrhoea, while others were blind and in a state of mania where they would just keep on walking until no longer able to stand.

There was no history of any changes to routine or treatment of these animals.

There are very few potential causes of these symptoms on a herd basis. The two main differential diagnoses would be ammonia or urea poisoning or lead poisoning.

With all fertiliser bulk-spread, there was no source of ammonia stored on farm. Another possible cause of some of the signs would be hypomagnesaemia or grass tetany, but this was very unlikely based on the large number involved.

Therefore, lead poisoning was number one on the list, but could not be confirmed without laboratory testing or a lead source.

We initiated symptomatic treatment of the affected cattle to alleviate clinical signs and took blood samples to check lead levels. I asked the farmer to check all the paddocks for a lead source.

A few hours later, the farmer called to say he had found an old battery in the corner of a paddock where bales had been stored for the last three years.

This area hadn’t been grazed in that period and the battery was split open with lead leaking. We got laboratory confirmation of the cause, with high blood lead levels and slivers of lead found in the stomach of the dead cow on post-mortem.

Lead is very palatable to cattle. Other potential sources include lead paint on old sheds and old lead piping. Lead weights are used on transponder collars and have been implicated in cases of lead poisoning also, where the casings have deteriorated over time.

In total, 10 cows died on the farm. Thankfully for the farmer involved, follow-up bulk milk and blood testing showed no increased lead levels in the rest of the herd.

Otherwise, potential losses in milk sales would be even more severe.

Sean Coffey works at Mulcair Vet Clinic, Newport, Co Tipperary, part of XLVets. See www.xlvets.ie.