Evidence-based decisions about when lambs need worming, and treatment choice when they do, are paying dividends for many producers, according to David Mulligan, Practice Manager, Parklands Veterinary Group.
“This not only protects flock health but will also help safeguard the efficacy of many different wormer treatments,” he told a parasitology training workshop at Strangford Lamb Group.
“An increase in the use of faecal egg count (FEC) sampling within the practice has created corresponding demand from clients for more knowledge in parasite control,” Mr Mulligan pointed out.
“Growing recognition by farmers of the ever present threat of wormer resistance on many sheep farms means we have seen a noticeable change in their attitudes to choice of wormer.”
Mr Mulligan explained how the concept of sourcing products on the basis that ‘it’s the same as Product XYZ only cheaper’ or ‘there’s a special offer on this pack’ was becoming outdated. He said replacing these were the responsible options of clinical diagnosis and treatment choice accordingly. Also speaking at the meeting was Zoetis vet Aurelie Moralis, pointing out that resistance to wormers is a genetic trait, so any resistant worms that survive treatment can pass this ability on to the next generation.
“As a rule of thumb, if more than five percent of worms survive, then resistance is starting to build up,” she explained.
“At that level though, there may be no outward signs in lambs to suggest reduced wormer efficacy. However, as resistance develops in the flock, the effects on health and production will become evident and eventually, potentially devastating.”
Cost of Resistance – ‘Stay Out Of the Red’
In the face of this threat, Ms Moralis reassured farmers that development of wormer resistance can be slowed by adopting responsible practices in the form of a four-point plan.
1) Find out the farm status
Knowing which products are effective is fundamental to controlling worms. Parklands vets will assist with determining farm status – a worm egg count after worming is straightforward to carry out. Early detection of reduced efficacy of a wormer means changes can be made to maintain effective worm control another way.
2) Protect your flock
All sheep farmers need to buy in replacements, so there is always the risk of bringing in resistant worms. It is essential that all sheep brought onto the farm - including rams - should be treated to remove worms, especially resistant ones. Even if there is some resistance already on your farm, quarantine is still advisable so as not to introduce worms which are resistant to other wormer groups.
For quarantine treatment, Aurelie recommended using a dual active product to remove resistant worms. STARTECT®, a broad spectrum wormer drench, is the first ever dual active wormer in the UK. It contains two active ingredients from different wormer groups. One is derquantel from an entirely novel wormer class and the second is abamectin, a wormer never previously available in the UK for use in sheep.
Both active ingredients are highly effective in their own right. Using a dual active wormer means that if one drug fails to kill all worms, the second can kill the survivors. Each active ingredient also helps to protect the other from resistance development.
After treatment, hold sheep off pasture for 24-48 hours without contacting existing stock. This allows any worm eggs present in the gut before treatment to pass out in the faeces and not contaminate the pasture.
Sheep should then be turned out onto contaminated pasture, which ideally was grazed by lambs as recently as possible. This means that if by chance a resistant worm does survive, its eggs will be diluted as much as possible among the pasture population, most of which are still likely to be susceptible to wormers.
3) Construct a Control Plan
Worming only when necessary helps reduce wormer costs and slows the development of wormer resistance, whilst maintaining lamb growth rates.
Work with your vet as part of your Flock Health Plan to follow a farm specific worm control protocol. Its suitability needs checking regularly in the face of uncontrollable changes such as weather. Fluctuating and sometimes unpredictable challenges through the season include varying levels of pasture larvae, and the volume of eggs passed from ewes or from lambs.
Lambs – the need and indeed justification for dosing can be very weather dependant, so use parasite forecasts and worm eggs counts to determine the optimum dosing time.
Ewes - consider treating around lambing time when their immunity to worms is significantly reduced and, as a result, many more worm eggs are present in faeces than at any other time of the year. These eggs add to the pasture parasite burden, and may therefore cause a problem for lambs later in the season. Meanwhile, leaving 10% of healthy, well-conditioned, ewes untreated slows the development of wormer resistance by maintaining the population of susceptible worms among which are diluted any resistant eggs produced by dosed ewes.
When working out the dose rate, do not guess live-weights. Instead, weigh a number of the biggest in the group. Otherwise, under dosing can select for resistant worms. When drenching, place the dose over the back of the tongue not just in the mouth.
4) Workshops and Advice
Bursary funding by the Parklands practice has supported a number of approved training events. These include Practical Sheep Lambing, Sheep Lameness, Safe and Responsible Use of Veterinary Medicines, and Sheep Parasitology.
The majority of these take place in specialist facilities at Parklands’ Cookstown branch, under the guidance of Patrick Grant MRCVS.
Training is broken down into various modules covering both endo- and ecto-parasites: considering the economic impact on performance; parasite identification; seasonality issues; product selection; diagnostic support; wormer resistance combined with practical steps relevant to each farm.
A key underlying message is the importance of making parasite control programmes specific to each farm. Recently, the practice has also developed strong links with a number of lamb producer groups who take advantage of the FEC sampling service and have enrolled members on training courses.
As a result of feedback from the Strangford Lamb Group for example, it was clear that there was sufficient demand to offer parasitology training at a convenient local venue.
David Mulligan can be contacted on: 078 3634 6908; Aurelie Moralis can be contacted on: 075 5707 6104.