The recent welcome rain is providing ideal conditions for parasites, especially gut worms, to thrive on pasture. This is contributing to the normal build-up of worm larvae on pasture that occurs each year as the season progresses, which can overwhelm animals, leading to clinical disease. First-season grazing calves, particularly dairy calves, are at highest risk of scour, weight loss or poor performance, so it is important to take action early.

The first step to controlling parasitic worms on the farm is to have a plan. It is never too late to do this, so if you do not yet have a farm-specific parasite control strategy for your herd, work with your veterinary practitioner to develop one. Equally, if a plan is in place, this is a good time to review it.

Different land types and management practices mean there is no one size-fits-all approach to parasite control. The monitoring of reduced performance and the use of diagnostic testing, such as faecal egg counts, will help to confirm that your control measures are effective.

Don’t wait until animals are showing clinical signs such as weight loss or scour to treat them, but this needs to be balanced against treating unnecessarily which can lead to an increased risk of anthelmintic resistance.

Adult animals do not usually need treatment for gut worms as they develop immunity over time. Younger animals are more at risk and should be placed on low-risk pastures that are likely to have lower numbers of infective larvae.

These are new or reseeded pastures, pastures that were not grazed by calves in the previous autumn or pastures that were grazed by sheep. It should be noted that effective grazing management can reduce the need for wormers.

Good dosing technique

Use the right dose – weigh the heaviest animal in a group and dose according to its weight. Split the group if there is a large weight range. Use a product that is specific for what you are trying to treat, eg don’t use a flukicide combination product if you are only targeting gut worms. Make sure to read the package leaflets, as products differ in their dosage, dosing guidelines and withdrawal periods.

More information on parasites in cattle and sheep is available on the parasite control section of www.animalhealthireland.ie.

Which animals need treatment?

Dairy

Dairy calves in their first grazing season have no immunity to parasites and need to be closely monitored as the season progresses. Ideally, graze these calves on low-risk pastures, such as aftergrass following silage. Faecal egg counts taken six to eight weeks after turnout, as well as monitoring average daily weight gain, can be used as an indicator for when calves might need treatment. Lungworm is unpredictable but is usually a problem later in summer and autumn. Monitor calves and treat as soon as they show the clinical signs of coughing or having breathing difficulties. If lungworm is a persistent problem on the farm, consider vaccinating calves, but this is advised prior to turnout.

Beef

While out on pastures with their dams, suckler calves are at low risk from gut worms. Worm eggs are consumed while eating grass, so spring-born suckler calves do not usually need gut worm treatments until weaning in the autumn.

If growth rates are below target alongside high numbers of worm eggs in a faecal egg count and calf nutrition is good, then wormer treatment is warranted.

Autumn-born suckler calves in their first grazing season are at a risk similar to dairy calves, as they may be exposed to high levels of pasture contamination but will not yet have developed any immunity. They should be closely monitored and treated when needed.

Second-season grazers should still be monitored even though they will have developed some immunity. If the worm burden is high, they can experience production losses and clinical disease.

Lungworm can also be a concern if animals weren’t adequately exposed in the previous season or were intensively treated for gut worms as they would be less likely to develop sufficient immunity.

Immunity

Cattle do not develop immunity to liver fluke and treatment around housing is usually advised for animals of all ages, especially for northwestern regions, if it is present on the farm. Roughly 10% of farms are free of liver fluke based on the Beef HealthCheck slaughter data, and this together with other indicators such as faecal egg counts or laboratory testing can be used to justify whether treatment for liver fluke is needed.

The Beef HealthCheck liver fluke data for your herd is available by logging in to the ICBF website, under the AHI animal health menu (www.icbf.com).

How to take a dung sample for a faecal egg count

1 Freshness is key to good-quality dung samples: they should reach the laboratory within 24 hours.

2 Keep the samples cool: they can be left in the farm fridge overnight if you are sending them the next day but do not freeze them.

3 Send samples at the beginning of the week: if they reach the laboratory late on Friday afternoon they may not be processed until Monday, decreasing the accuracy of the test. Lungworm testing requires an overnight process so these must reach the laboratory by Thursday each week.

4 Take samples from the fresh dung of 10 to 15 animals: approach the group when they are resting as they will often pass dung as they walk away.

5 DISTRIBUTION: take a small amount from various parts of the dung pat mixed together for one sample because the parasite eggs are unlikely to be distributed evenly throughout the dung.

6 LABELLING: collect 10g to 40g of dung per animal, roughly the size of a golf ball into individual containers and label them to distinguish between animals.

7 Ensure the sample containers are leakproof: your veterinary practitioner or laboratory can provide screw cap containers.

8 results: discuss the results with your veterinary practitioner as the interpretation is not always straightforward.