DAIRY farmers in England could be losing up to £178m a year because gutworms are reducing the milk production of grazing cows.

Tests on bulk milk samples last year showed 92 per cent of the herds tested had been exposed to a high gutworm challenge.

If the finding, produced from MOO tests, is spread across the national herd, it means more than 1.1 million cows could be affected.

The tests were carried out on 358 farms across England and measured levels of antibodies to gutworms in the milk.

Elevated levels of antibodies show cows are exposed to a high gutworm challenge – only six per cent showed a medium level and only two per cent a low level.

Research has shown that removing these gutworms with Eprinex Pour On, milk production can be increased by up to two litres per cow per day.

This means that, by leaving cows untreated, dairy farmers across England may have lost out on nearly 754m litres of milk last year, worth approximately £178m.

Fiona MacGillivray, Merial veterinary advisor, said: “Many dairy farmers don’t believe that gutworm burdens are a problem as they cause no obvious clinical effects in the adult cows.

“However, there is an abundance of independent research in more than 5,000 dairy cows across the world which clearly shows that worming cows with eprinomectin improves both milk production and fertility.”