Cattle farmers are being advised to treat for fluke as soon as there is a risk presented, rather than wait until housing.
A spell of warm and wet weather could give rise to an earlier fluke challenge, and leaving treatment until housing could result in unnecessary production losses, as well as causing continued pasture contamination.
Zoetis vet Dr Dave Armstrong says: “A cow’s liver is bigger, so can tolerate a greater fluke burden, so you will not see sudden deaths like you would in sheep. However, you will see subclinical disease, which can be costly.
“It is important to remember both immature and adult fluke cause production loss and, therefore, waiting to treat until housing is counterproductive if you have fluke on-farm.”
Fluke infected cattle can take 80 days longer to reach slaughter weight, costing £25-£35/head, according to AHDB figures.
Studies show reduced reproductive performance in bulls, reduced conception rates in herds, increased age to first oestrus of 39 days and, in adults, an increased calving interval of 4.7 days on affected farms.
All farms containing wet areas could be at risk of fluke, as it is those conditions which favour the fluke’s intermediate host, the mud snail.
When selecting treatment options mid-season, farmers need to consider the age of fluke they are treating for.
Many fluke treatments focus on killing egg-laying adults, meaning most immature fluke will still be present. These will continue to cause damage as they migrate through the liver and will go on to develop into adult fluke.
A dual-purpose product containing moxidectin and triclabendazole has been found to be 90 per cent effective against early immatures, 99.5 per cent effective against late immatures and 99.9 per cent effective against adults.
This is compared to products containing closantel, which only killed 26.8 per cent of early immatures, 90 per cent of late immatures and 99.3 per cent of adults.
Dr Armstrong says: “Your adviser will be able to give you the best advice of which products to use, depending on your farm’s situation.”
No fluke treatment has persistency, meaning cattle can become infected with fluke immediately after treatment if they are grazing contaminated pasture.
Dr Armstrong says: “This is why it is important to treat again at housing, regardless of whether you have treated mid-season.”
Treating at housing will control fluke picked up during grazing, enabling a better housing transition.
Dr Armstrong suggests using a flukicide at housing with the widest spectrum of action and retreat as necessary during housing to turn out clean, fluke-free cattle next year.
He says: “It is important to manage fluke on-farm rather than focusing on individual animals. Turning out clean cattle will reduce burden on the pasture and help protect any sheep on-farm.”
Farmers can monitor fluke and worm levels in their area by clicking on an interactive map found at www.parasitewatch.co.uk