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Video 34 Managing cattle parasites in the first grazing season


The background

Cattle parasites are one of the big challenges in grazing systems. The first grazing season can often be the most problematic. There are a number of parasites that can challenge dairy and beef calves in their first season.

While I will deal with the management of both separately there are some common challenges.

The main parasites in the first season are roundworms like ostertagia and cooperia. A huge challenge is also lungworm and I think this needs to be revisited on its own. With most 1st grazers liver, fluke is a low risk until later in the season. This can depend on the overall risk on the farm.

With our roundworms, cattle can develop a natural immunity over time. With liver fluke, no such immunity develops. Some farms also have to deal with rumen fluke in younger animals.

I will visit the fluke parasites in a later blog.

The lifecycle

When we talk about roundworm control we must remember the basics of the lifecycle. Part of this is outside the animal and the 2nd half is inside. Outside the animal, the young worm (larvae) must develop into the infective stage. This can take from 1-3 weeks depending on the conditions. Inside the animals, this is where the strategic use of workers can help our control of parasites.

The challenge as the season progresses we can have large numbers of infective larvae on pasture. This can depend on a number of factors. The weather is something that can play a role. Dry hot weather doesn’t suit larvae and will slow down pasture larval levels. With mild wet weather being absolutely ideal for most of our roundworms including lungworm.

In the video above I talk about some of these risks.

Clinical signs

The classic symptoms in young ruminants with gut roundworms are loss of condition. They may be scouring or have loose faces, they can be underweight and showing poor growth and thrive. Always investigate poor thrive in young cattle at grass. Consider nutrition, minerals and other parasites like coccidiosis.

Cattle with respiratory symptoms consider lungworm, other bacterial and viral infections.


Grazing patterns

In pasture-based systems, good grass growing weather is the exact same conditions that roundworm parasites like. We can overcome this challenge by looking at how grazing can be adapted to reduce down our parasite challenge.

I have spoken to two farmers who recently started growing mixed-species swards and seen a reduction in parasite issues. While research is ongoing in this area it is quite exciting.

Farms, where calves are co-grazed with sheep, reduces the risks for roundworms but may increase the risk for fluke and nematodirus. For dairy calves, we can look at where we turnout calves to each year. The like of training paddocks for examples can create risks each year.

Be brilliant at the basics

We need to have the fundamentals right before we talk about parasites. We need a healthy growing animal and healthy rumen. We must of course focus on good rumen health and nutrition. We also need to manage the essential minerals during the grazing months. Some of the key ones are

  • Copper
  • Selenium
  • Iodine
  • Cobalt


Talking worms

The products

For years we controlled worms effectively with anthelmintic products. We have three main worm products or active ingredients.

  • White doses: these are the benzimidazoles and are generally an oral dose for calves. They cover all stages of larval development.
  • Yellow doses: these are the levamisole’s which again are generally oral doses with an injectable form as well
  • Clear doses: these are the macrocyclic lactones or more commonly known as the ivermectins. These can be given by many routes and have persistency in the length of their action

While individual product selection on-farm is a conversation for your own vet. They do play a significant role in control. We need however to reduce down our usage.

Worm resistance

An increasing challenge on Irish cattle farms in the development of anthelmintic resistance. This is where the parasites become resistant to killing mechanisms of the doses we traditionally have used to kill them.

With no new anthelmintic in the pipeline, we need to consider how we spare and use these existing products better.

We need to manage the external factors like weather grazing and diagnostics. We then need to use farm-specific products that not only suit (labour) but also the slow down of resistance.

Resistance develops faster when we overuse or misuse worm doses.

We really need to make sure we dose by weight and avoid underdosing. Use the products correctly and by the right route.

Look at rotating dosing classes between seasons where possible. Use faecal egg count reduction tests to monitor if resistance may be an issue on your farm.

Some tips for suckler calves

With suckler calves, we have a longer window before initial dosing may be required. When they are suckling the risk of parasites is lower. We need to time our doses based on need.

Typically calves don’t show issues with worms for 6-8 weeks post turnout. we need to start using three tactics in worm control

  • Pooled or individual faecal egg counts to monitor egg numbers in dung
  • Clinical signs of scour or ill thrift
  • Monitor daily live weight gain (set your target)

My suggestion to suckler farms is begin with doing pooled faecal samples every 3 weeks from 6-8 weeks. Use these results with weights and close monitoring of clinical signs.

What this will do on most farms is reduce down the number of doses. Watch the weather conditions and be mindful of risks around grazing strategies.

The future of parasite control will be also dosing animals selectively where we factor in the need for a dose. When animals in a group are thriving they may not need a dose.

This certainly makes parasite control more complex than the security blanket of dose and move.

We must factor in also the labour efficiency on the farm.

Faecal egg counts can be carried out with patience in the pasture. Picking up fresh samples while walking through your stock. When we get calves up from lying down they will often defecate.

While long-acting pour on and injectables work really well. We need to be mindful of rotating antiparasitic products between years.

We need to be mindful to watch out for other parasites like coccidiosis as well.

With no new wormers in the pipeline, we need to be more proactive and preserve the ones we have.

Some tips for dairy calves

The big challenge for dairy calves is we need to be on our guard at a much earlier stage of the summer months. They are grazing earlier and sometimes through grazing strategies may have increased risk to infective larvae at pasture.

Monitor turnout and grazing strategies each year. Particularly after short mild winters with the early turnout, we could have larger numbers of overwintered parasites.

Faecal egg counts are very valuable in younger grazing animals. Pooled faecal samples allow us to cut down cost while still using them as monitoring tools.

With nutrition and minerals also being key things to get right. We need to look out for other issues like summer scour syndrome also.

My tip for dairy farms is to begin pooled faecal egg counts earlier after 3-4 weeks of turnout and monitor them every 3 weeks at a minimum.

For lungworm control, we need to take into account other factors especially clinical signs.

With DLWG (daily live weight gain) being such an important tool we need to regularly be monitoring this over the summer.

React fast to poor thrive or any clinical symptoms like scour at grass. Don’t ignore dirty tails and monitor dungs during your stock checks.

At the very minimum when symptoms appear make a diagnosis to make a difference. Get faecal egg counts from calves underweight or with any symptoms.

Rotate dosing between years and look at using white doses early on in the season to allow some immunity to start naturally develop. Some long-acting macrocyclic lactones will also allow immunity to develop but where they are being used repeatedly seasonally monitor for resistance.

Get a handle on worm resistance on your farm by checking faecal egg count reduction tests.

Do this by sampling calves before dosing using FECS.

Then after dosing take another sample

With white drenches resample at 10-14 days

With clear (macro-cyclic lactones0 it generally is 14-16 days

With yellow drenches sample at 7 days

We are looking for a reduction in these egg counts of greater than 95%. between before and after.



This for most farmers will seem like a lot of work. However, parasites are now becoming a real potential limiting factor in some of our grazing systems. We have no new products in the pipeline and must use the ones we have more sparingly. With new legislation set to potentially make these products prescription-only medicines we need to be mindful of how and when we use them.

With lungworm being such a huge issue I’m going to cover this in a later blog on its own.

Thought for the day

Never be afraid to think differently. Creativity is intelligence having fun

Huge thanks to Nettex for helping me develop #50in50 for more information click on the link here http://www.net-tex.co.uk


Happy safe farming

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