Swollen hocks and teat-end oedema in dairy cows are easily visible indications of a possible mycotoxin threat and should prompt action to deal with feed contamination, according to Alltech's UK ruminant technical manager David Wilde.

These symptoms are being seen on farms this winter, he says, and the mycotoxin fusaric acid - which is produced by fusarium mould - is being identified as a cause. He said: "Fusarium is one of the moulds that can be present in feed, and a number of factors such as the use of higher dry matter forages and this year's wet cereals harvest have led to an increased incidence. Fusaric acid is just one of a number of potentially harmful mycotoxins that fusarium produces, and it has an effect on the animal that ultimately leads to low blood pressure.

"Low blood pressure can cause blood and lymph fluids to build up in the lower extremities - specifically the legs and mammary tissues - and this leads to the characteristic swellings. When housed, cows tend to stand up far more and have relatively little exercise, so there is a greater chance of the reduced blood pressure causing a problem.

"Fusaric acid also causes the brain to produce seratonin, which is a natural sedative. This causes lethargy, which in dairy cows will lead to depressed intakes and reduced milk yields, and will further exacerbate the lack of exercise and loss of blood pressure."

Mycotoxins are difficult to identify in feed. Mr Wilde says treatment with a mycotoxin-binding feed additive may be a more cost effective solution than extensive feed analyses.