COWS – Consider which products to use when treating cattle for parasites this winter
Robert Smith, director at Farm First Vets, Abergavenny and a member of the Control of Worms Sustainably (COWS) steering group, urges farmers to consider the effect treatments they give for internal parasites at housing might also be having on skin parasites.
“Most cattle producers apply a pour-on macrocyclic lactone (ML) anthelmintic at, or just after housing, to control gut worms and lungworm. These products also kill lice and mites,” says Mr Smith.
“But what if the treated cattle do not have a skin parasite problem, or only have them at levels low enough to have no ill effects? Using broad-spectrum products in this situation could be wasteful and encourage the development of resistance by any lice and mites that are treated.
“An alternative approach would be to give cattle a different class of wormer such as a white drench, which generally has good activity against gut and lung worms. Then only treat lice and mites if they are causing problems later on, with a product specific to them, for example a permethrin pour-on.
“Pour-on MLs are used by many farmers throughout the grazing season to control gut and lungworms, so using a different class of wormer at housing will help slow the development of resistance to MLs on the unit.”
Low numbers of lice – both chewing lice that feed on skin and hair, and sucking lice that feed on blood, are almost normal inhabitants of the dermis and the coat of cattle, especially in winter. Louse infestations can increase very rapidly and moderate infestations can be associated with mild chronic skin inflammation, but these are often well-tolerated. In heavier infestations there is intense itching with rubbing and licking and the welfare of the animal can be compromised. Heavy infestations often indicate an underlying chronic disease or nutritional issue.