Managing Parasites in Dairy Cows at Housing 2013

Despite a relatively dry summer, there is still a large burden of parasites on grazing swards. Housing is a good time to treat cows as they are not exposed to fluke or worms once housed. Don’t forget to also treat for external parasites (lice and mange). Selection of the correct product or combination of products will save time and money.  Remember to follow product instructions carefully and give the appropriate quantity of the dose to each animal.  Weigh cows to ensure you are not under-dosing.

Key points:
• Don’t be complacent due to a dry summer. Fluke and worms are present in large numbers on grazing ground; housing is an excellent time for treatment.
• Ensure to follow product instructions carefully including weighing cows to avoid under-dosing

Parasites to target at housing
1. Liver Fluke

There is a traditional perception that a “dry” farm is not at risk from liver fluke. Recent studies by Teagasc Moorepark has shown that the absence of a fluke control programme, statistical analysis showed that there was no difference between farms classified as “wet” or “dry” in terms of liver fluke levels.  In fact “wet” farm herds tended to have less liver fluke problems because they routinely implemented an effective liver fluke control programme including annual dosing of animals at housing.

Key point: Liver fluke is widespread; don’t assume you don’t have a problem just because you have a ‘dry’ farm. Unlike with worms, adult animals cannot build up immunity to liver fluke.

Only flukicidal veterinary medicines containing Triclabendazole (Fasinex 240 only), Oxyclosanide (Zanil only) or Albendazole (e.g. Albex and Endospec), can currently be used to treat fluke in animals which are intended for milk production. In these cases, the appropriate withdrawal periods indicated on the product labelling should be strictly followed.  Table 1 shows the cost per treatment of the different options for Dairy cows.

Key point: Fasinex 240 is the product of choice against liver fluke as it is active against adult, immature and early immature fluke while other product options available to dairy farmers are only active against adult fluke only, leading to the requirement for a two dose programme.

2. Worms
Cattle built up immunity to gut and lung worms as they get older.  Therefore it may be unnecessary to treat adult cows.  However, due to the high levels of grazed grass in the diets of dairy cows in Ireland, a high worm challenge is often present meaning a production penalty in terms of milk yield, body condition score and fertility.  It seems to be more prevalent in first calvers & higher yielding cows and these animals should be targeted for treatment.  Eprinex (zero milk withdrawal) can be used to treat cows at grass or cheaper products can be used at housing (but watch withdrawal times)–use products that are effective against Type 2 Ostertagia and are cleared for use in dairy cattle.  

Key point: The majority of livestock, including dairy cows, are likely to require a worm dose at housing. At a minimum target first calvers & higher yielding cows for a worm dose at housing. Make sure your housing wormer covers type 2 Ostertagia and is cleared for use in dairy cattle.

Lice (biting and sucking)-all animals should be treated at housing and a repeat treatment may be required 5-6 weeks later.
• Plus/minus Rumen fluke- only treat where rumen fluke has been detected in combination with clinical signs. Small numbers of rumen fluke are unlikely to cause much damage.  Routine dosing is rarely justified.

3. Lice and Mange
Numbers can build up rapidly in housed cattle.  Ivermectin products that kill worms are suitable but note injections will not cover biting lice (sucking lice only) while pour-ons do.  Specialist pour-on products are also very effective e.g. Spot-on.

Key point: Injections will not cover biting lice, a pour-on is required for complete cover

Plus/Minus Rumen Fluke
The new threat of rumen fluke has developed in several areas around Ireland.  Currently Oxyclosanide (Zanil) is the only active ingredient known to be effective against rumen fluke that is licensed for use in dairy cows.

• Options 1 and 2 are recommended as they are more effective against liver fluke (full kill at much earlier stage), less stressful on the animals and less labour intensive.
• For options 1 or 2 best to wait until two weeks after housing before treating with Fasinex 240 to give complete control of liver fluke
• For options 1 or 2 add Zanil for Rumen Fluke if required (do not treat with two fluke products on the same day-leave two weeks between applications)
• For option 3 use Zanil for Rumen Fluke if required instead of Albendazole for second fluke dose (covers rumen and liver fluke but again do not treat with two fluke products on the same day-leave two weeks between applications)

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