PARASITE CONTROL AT HOUSING
(Ref. Animal Health Ireland Parasite Control Technical Working Group)
As we approach the time of year when farmers are preparing for or starting to house their animals, it is important that a plan for parasite control is put in place.
Herds that have used diagnostic sampling through the summer may have needed minimal dosing; however, animals should be treated for parasites at housing unless diagnostic tests (dung samples or blood and milk samples) specifically show otherwise. Housing is an excellent time to carry out parasite treatment, as animals cannot pick up new worm or fluke infections until turn-out to grass next spring. Thus, effective anthelmintic treatments at or during housing should keep the animals virtually free of worms and liver ﬂuke until they return to pasture the following year.
The target parasites for cattle of all ages at housing are stomach worms, lungworms, liver ﬂuke, chewing lice, sucking lice and mange.
• The instructions on product labels should be followed closely.
• When dosing, it is good practice to weigh a number of animals to ensure the correct dosage volumes are used, and to check the calibration of dosing guns. Under-dosing can lead to a build-up of anthelminthic resistance.
• For gutworms, products active against both adult and inhibited larvae of the stomach worm, Ostertagi can be recommended.
• Externally applied products are suitable for the treatment of lice. If high levels of control are required, all animals in a group should be treated, ensuring they are not in contact with any untreated animals throughout the winter.
• Injectable products can be recommended for sarcoptic and psoroptic mange.
• If using flukicides at housing that are only effective in treating older immature liver flukes and/or adult liver flukes, then faecal samples should be checked approximately 6-8 weeks after housing to see if any liver fluke eggs are present, retreating if appropriate. Alternatively, dosing with these flukicides can be delayed to 6-8 weeks after housing, by which time most of the liver fluke present in the animal will be adult and therefore susceptible to treatment.
• Animals should only be treated for rumen fluke following a definitive diagnosis and if they are showing symptoms of rumen fluke infestation.
• When treating dairy cows at drying-off or during the dry period, ensure that withdrawal periods are complied with.
• Cattle can pick up parasites if turned out to pasture over winter, even for a short period following housing. In these circumstances it may be necessary to repeat treatment.