Check sheep weights to get quarantine dose right

With sheep now arriving on farms from sales all over the country, quarantine strategies, including preventing anthelmintic resistance, should be the prime thought for most farmers.

But unless quarantine drenching, including treatment with both a levamisole drench and either an injectable macrocyclic lactone or a macrocyclic lactone drench, is done at the correct dose, it could accelerate resistance occurrence.

But if the results of a Novartis-sponsored competition held at Sheep 2006 are replicated on farms across the UK, it is likely many farmers will be underdosing sheep when administrating quarantine doses this year, says independent sheep consultant Lesley Stubbings.

“More than three-quarters of farmers entering the competition underestimated the weights of sheep in three groups at the event, with 40% guessing a weight more than 10% below the real weight.”

And although these results are in line with other data, Ms Stubbings says they again highlight the importance of weighing sheep before dosing. “Underestimating the weight leads to underdosing, which significantly speeds up the development of anthelmintic resistance among worms,” she says.

“The drive among the industry to eradicate sheep scab makes this vital, because failing to give the correct dose of an endectocide risks resistance among scab mites, too.”

Suffolk farm manager Michael Mumford says the need to manage replacements as a separate group and ensure all quarantine treatments are done rigorously is justified, particularly as he has seen problems in bought-in stock.

Mr Mumford reckons there can be no excuse for failing to exercise a proper quarantine strategy. “No matter what vendors say at sale time, we always practise the same plan.

Ewe lambs are dosed with a fluke and worm combination drench and then treated with an injectable scab product, too. We also treat them to prevent any foot problems coming on to the farm, including CODD and footrot.

“We are lucky to have a block of land about seven miles away from the main holding with its own handling facilities where we can isolate new stock. Any equipment used with these sheep is washed and disinfected thoroughly before we take it back to the main farm.”

This does create extra work, but Mr Mumford says it is worthwhile because it means he has a group of shearling replacements of known health status the following year.