With the change to wetter conditions, worm burdens will be increasing on grazing ground putting young cattle and lambs at risk.

If you delay treating animals for too long, then animal performance will drop leaving you with lighter cattle at weaning and housing.

Gut worms (Osteragia) are most common in calves and yearling cattle during the summer months from June to September. Once ingested, they affect the animal’s stomach and intestines and cause gastroenteritis.

Symptoms include calves having prominent watery, green diarrhoea. Animals can also suffer a loss of appetite and a rapid weight loss of 10% to 20% within a 10 to 14-day period.

Young animals in their first grazing season have no natural immunity to gut worms. Older cattle groups in their second season have some resistance, but will still be at risk of picking up a heavy worm infestation.

Mature cows tend to be less at risk as they will develop some form of immunity to these worms over time.

Lungworm

Lungworms (hoose) are also a problem in spring and autumn born calves, but generally it is more of an issue from mid to late summer onwards.

However, unlike gut worms, older cattle in their second grazing year tend to develop immunity to lungworm.

It is most common from July right through to late September.

Warm, humid weather creates ideal conditions for lungworms to multiply rapidly, especially if these conditions follow rainfall.

The most common characteristic of lungworms is the harsh coughing in young cattle, followed by heavy breathing from the onset of pneumonia.

Risk period

Parasites such as gut worms need cattle to complete their reproductive cycle. Worms are ingested by grazing animals, with larval eggs then laid in the digestive tract of cattle and sheep.

These eggs are excreted in faeces and then hatch and are again ingested by grazing animals where they mature and start the cycle again.

With more animals on grazing ground, the multiplication rate of a worm burden quickly increases, as does the risk of parasite exposure to younger animals.

Treatment

Most farmers will routinely treat animals for worms, but timing and product choice are important.

Treating too early means there will not be an effective kill and shorter residual cover period. Treat too late and animal performance has already been affected.

To reduce the build-up of anthelmintic resistance, you should alter the products used to kill worms in livestock. Repeated use of the same product will eventually reduce how effective it is.

For best worm control, follow the outlined steps.

1. Faecal egg count (FEC)

If there are no visual signs of a worm problem, use a FEC to determine when animals need to be dosed. Routine dosing offers little benefit if there is a low worm burden present and will increase anthelmintic resistance. Take 10 to 12 fresh dung samples from calves, stores and lambs for each FEC. Use a FEC test to monitor how effective the wormer was at killing eggs.

2. Delay first dose

To encourage natural immunity to worms, cattle need to have some level of exposure during their first grazing season. Delay dosing spring born calves until mid-June so that worms will have completed a full-life cycle in the animal. Normal dosing routine should then be followed.

3. Weigh cattle at dosing

Guessing the weight of an animal means there is a risk of underdosing cattle. Therefore, animals will not be properly treated.

4. Dose to the heaviest animal

If you cannot weigh cattle, group cattle to size and set the gun to the heaviest animal in the group to give effective treatment cover.

5. Apply pour-on properly

Run cattle through a race so that a pour-on drench can be correctly applied to cattle on the back.

6. Do not dose and move

Rather than moving animals to clean pasture after dosing, return cattle to the paddocks they were in for another two to three days to reduce contamination of clean grazing.

7. Mixed grazing

Mixing cattle and sheep helps to dilute the worm burden on pasture. As mature cows have natural immunity and can consume larger quantities of grass, they will also ingest high levels of worm eggs reducing the worm burden for younger animals.

8. Follower leader grazing

Where calves or lambs are weaned, a follower leader system can help to offer clean grazing to young stock. Allow calves and lambs to graze for one to two days before moving onto the next paddock. Use cows to clean out the paddocks afterwards.

9. Change wormers

Rotate worming products to reduce resistance and get a more effective kill and cover period.

10. Put bought-in stock onto contaminated pasture

Bought in cattle have a different health status to home bred animals. Put bought-in animals onto “contaminated” pasture until they have been dosed.

Withdrawal period

Always check the withdrawal period before dosing animals. Where fat lambs will be ready for sale in the coming month, dosing could delay sale date, and lambs can then run over weight.

The same applies to beef cattle that will be finished off grass this summer.