16 August 2002

Egg counts fine-tune drench timing

Faecal egg counting

provides an excellent tool

to improve timing of

anthelmintic drenching. But

it is vital results are

correctly interpreted.

Several large sheep farms

have been impressed by a

consultancy service offered

to them this grazing season.

Marianne Curtis reports

REGULAR faecal egg counting has brought savings of at least £600 this grazing season through reduced drenching and allowed better planning of labour resource on one 1600ha (4000-acre) Lincs unit.

Lambing throughout March, Percy Gilman aims to get the creep fed first one-third of lambs from his 4000 Mule ewe flock away by mid-July. So it is vital they suffer no growth check.

"In previous years we have wormed this group of lambs by mid-May using Cydectin and again using cheaper drenches in early June. Then drenching was at three weekly intervals until lambs were sold."

But this year independent sheep consultant Lesley Stubbings persuaded Mr Gilman of Manor Farm, Tixover, near Stamford, to adopt a different approach. "There is a tendency for shepherds to pile in and drench in late April/early May because that is what they have been told they should do. But this can be unnecessarily early," she says.

This theory is borne out by results from several of Ms Stubbings clients – who produce 22,000 a year lambs between them – including Mr Gilman. Faecal sampling began on the farm on Apr 26, with 10 lambs from each field sampled.

Unlike other recommended faecal egg counting techniques, where pooling faeces from different lambs is common, faeces from different lambs is kept separate.

"This improves data interpretation. For a group of 10 samples you could have a nematodirus average count of 300 resulting from two lambs with counts of 1500 and eight with zero. In a pooled sample you would have no clue whether all lambs had significant counts or only a couple."

Mr Gilmans first results showed few lambs with nematodirus; an odd one with a count of 50 in a couple of fields. Coccidia – the other important parasite to monitor at that time of the season – was also below the threshold where problems occur. On this basis, in consultation with Kym Abbott, at the Royal Vet College, Ms Stubbings suggested drenching at this stage was unnecessary. "I agreed and, at a conservative estimate, we saved £600 on drench. We also saved about a weeks labour and avoided stressing lambs when they were only six to eight weeks old," says Mr Gilman.

The lamb crop suffered no set-backs through missing the drench and creep-fed lambs were sold finished by mid-July.

Missing the first drench, where appropriate, may also allow lambs to build better natural immunity to worms, suspects Ms Stubbings.

"By targeting drenching more effectively, we will also delay the onset of widespread anthelmintic resistance in UK sheep flocks."

Knowing the optimum time to drench also allows Mr Gilman to plan labour resources more effectively. "When someone is going on holiday, counts help us decide whether it is necessary to drench lambs before they leave or whether they can safely wait until the person returns."

Each group of lambs is sampled every 3-4 weeks and egg counts can vary widely between fields, even on the same farm. Mr Gilmans lambs are grazed mainly on permanent pasture, so worms have more chance to build up than on generally cleaner short-term leys.

"More and more sheep are grazed on permanent pasture with little use of leys. We know worms are there, but counting tells us when lambs are at risk. This will vary from season to season, so counting will be necessary through every grazing season," he says.

Sending samples for counting has been easy, with results returned promptly allowing early action where required, says Mr Gilman. "Sheep are run into a field corner and we opted to take samples directly from lambs as it can sometimes be difficult to differentiate between freshly dropped ewe and lamb faeces."

For this project, the Royal Vet College is supplying plastic bags, labels and a prepaid envelope. Ms Stubbings receives results within 24 hours of posting samples and is able to advise clients on worm control strategies immediately.

"Getting results back quickly is important. Unfortunately, it can sometimes take a while via vet practices. Also, interpreting results from a number of farms helps me build up a picture."

Sampling has cost Mr Gilman £150 so far this season. "It will be no more than £200 for the whole grazing season and I plan to do it again next year. It allows decisions about worming to be made based on fact, rather than guesswork."

PARASITE MONITORING

&#8226 Better targeted drenching.

&#8226 Lower labour requirement.

&#8226 Reduces anthelmintic resistance.