15 October 2015

3 minute read

That is the message from Dr Johannes Charlier, winner of the Peter Nansen Young Scientist Award at this year’s WAAVP. He believes that worming is often carried out according to a routine that is easiest for the farmer to follow, rather than most beneficial for the cows.

“The problem is that the treatment is easy and farmers can go ahead and do it themselves. There is too little involvement of the vet. The decision should come from both sides: the parasitology and health background from the vet, and the economic knowledge of the farmer.

“You cannot give a general recommendation for all farms. You cannot just de-worm twice a year and expect no problems. You need to take an approach based on data and a discussion between the vet and the farmer.

“If the worm load is low you don’t have to worry, but if it’s higher then it makes sense to evaluate what needs to be done and how best to do it.”

Dr Charlier believes that worming cows individually when they are in the dry period is a good option for many farms, but points out that this does require more organisation than simply treating the whole herd at once. The aim should be to make worming an integral part of the standard herd management system by perhaps combining it with some other dry cow routine.

Worming around calving is one option because the benefits in terms of increased milk yield can be up to 1kg/day per cow, he says.

“In Europe about 50% of dairymen don’t treat adult cows at all, and of those that do, most do it in the summer or at housing. No more than about 15% of farms are worming at calving, even though from an economic point of view that would be better.”

Although dairy worming could be improved in Europe, Dr Charlier points out that 10 years ago almost nobody was treating, and the advent of new efficacious anthelminthics with a zero-withdrawal time for milk, has meant that far more cows are now being treated.

“In most countries eprinomectin and moxidectin have zero or very short withdrawal times for adult cows and these are the best option,” he says. “There are some benzimidazoles which have short withdrawal times and you could use those in the dry period. They are cheaper but they have a lower efficacy against immature stages of the Ostertagia parasite and the effect will not last as long.”

Dr Charlier says that pour-on formulations are preferred by most farmers because of the ease of application which means farmers can administer the treatment themselves and more quickly. However, in some cases this can result in underdosing due to licking behaviour of the cows and influence of weather conditions (exposure to sun light and rainfall).

Farmers who want to assess the need for a better worming programme can ask their vet to assess the current exposure of their herd to parasites using an ELISA bulk tank test.

“Look at the evidence for your farm and take your own decision. There is a lot of science out there, but you have to see how that science fits into your particular farm. Science is based on averages and will not be representative for your particular farm, so use the specific figures, such as ELISA test and grazing management, to decide what to do.”

Dr Johannes Charlier is a veterinarian from Belgium with a particular interest in cattle parasitology and its impact on commercial herds. He has worked at the Laboratory of Parasitology at Ghent University and conducted research into the diagnosis, epidemiology and economics of helminthic infections in cattle, including a number of EU-funded international projects. He is founder of ParaCalc®, a website offering tools to support the control of parasitic infections in livestock and he recently joined Avia-GIS, with the aim to bring decision support systems in animal health from research to practice.