By Debbie James

Testing heifer dung for worm eggs on-farm is giving dairy farmers instant and accurate results to inform rapid dosing decisions.

As pressure grows on farms to tackle anthelmintic resistance, more dairy farmers are using faecal egg counting (FECs) to establish the level of worm burden in their youngstock and to identify which parasites are present.

The most common approach is for samples to be analysed by veterinary practices or laboratories but, with training from their vets, more farmers are now doing their own testing because this gives them immediate results.

It also means that samples are fresher when they are tested – faeces must be analysed within 48 hours to prevent destruction of the eggs and a false result.

On-farm testing requires a microscope – prices can range from £300 to £1,000 – and associated apparatus but this can be recouped from money saved on laboratory fees, reckons Pembrokeshire-based heifer rearer Claire Watts.

After undergoing training with a vet, she has the confidence to analyse samples.

Counting worm eggs is straightforward, she says, although interpretation requires further knowledge of the parasite lifecycle and risk factors for the animal.

For this reason, when a farm first starts to use FEC results in a worming programme, it is advisable to discuss results with a vet or animal health adviser.

Factors such as age, condition, forage quality, time of year and weather are some of the considerations which need to be made.

If eggs are present but at a low level – less than 200 eggs per gram – Ms Watts says stock are not wormed as this allows immunity to build up; the animals are monitored closely during this time and FEC is then repeated.

If a higher number of eggs are present, the group is wormed.

FEC is repeated when the wormer cover has run out.

The test is also used to identify coccidiosis.

The dairy sector has lagged behind the sheep industry on adopting FEC but this mindset is now changing.

Vet Lara Robinson, of the Wrexham-based Daleside Veterinary Group, says in the past dairy farmers haven’t always had access to the evidence they needed to inform their worming decisions.

“They’ve dosed on the presumption that an animal has a worm burden and have blindly chosen a product to use.

“FEC is important in the sense that just like bacteria can develop resistance to antibiotics, worms can become resistant to wormers.’’

Ms Robinson says outsourcing FEC is straightforward and relatively low cost but that with correct training it is a job farmers can also do themselves.

She recommends testing between 3-4 weeks after turnout and monthly thereafter.

It is also advisable to sample 3-4 weeks after housing, she adds.

“It is fairly common practice to blanket treat at housing and it can be a useful, low-risk way to deal with the worm population but from a cost point of view there is no point in using a product if it is not needed.’’

The samples should be fresh and not stored at high temperatures because larvae are sensitive to temperature changes.

“Don’t leave the samples in the sun or in the boot of a car and get them tested as quickly as possible,’’ says Ms Robinson.

She advises taking 10-15 samples from a group, and pooling the samples while ensuring an equal mix of samples.

“If you take a large sample from an animal that doesn’t have a worm burden and a small sample from one that has a significant infestation the egg count will be diluted therefore the result won’t be accurate,’’ she points out.

It is also important to select samples at random.

“With a group of youngstock it can be useful to randomly select 10-15 animals – perhaps using their ear tag numbers instead of their visual appearance as there can be a tendency to select the best or worst looking animals – and to run them on a small area of pasture for a couple of hours and collect samples from the fresh pats.’’