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Cattle at grass are now facing a growing health challenge from parasites such as gut worms and, if left untreated, there will be a considerable drop in animal performance.
Young cattle in their first grazing are at most risk, but growing cattle in their second grazing season will also require a worm drench.
First-calved heifers will also benefit from a worm dose now, as the physical demands placed on the animal during the early lactation and breeding period can suppress the animal’s immune system and leave it more susceptible.
However, mature cows will have developed immunity and therefore, will not require any kind of worm drench at present.
Risk period
Worm populations on grazing ground will be increasing rapidly due to recent rain. Parasites such as gut worms need cattle to complete their reproductive cycle. Worms are ingested by grazing animals, in which they mature and lay larval eggs in the digestive tract.
These eggs are then excreted in cattle faeces, before hatching, and starting the cycle over again.
Types of worms
Roundworms (Ostertagia and Cooperia) mainly affect young grazing cattle from June to September. Once ingested, the worms cause damage to the animal’s stomach and intestines, causing gastroenteritis, which usually can be identified by a watery, green diarrhoea.
Cattle with a heavy burden of worms also suffer from reduced appetite and rapid weight loss, anywhere from 10% to 20% within a 10- to 14-day period.
The second type of worm burden to affect cattle is lungworms (hoose) and it is more of an issue in late summer to early autumn.
However, if conditions are right, it can still be an issue in June and July. It can be easily identified by the dry, rasping cough.
If this is not treated in time, cattle will often develop pneumonia, which causes further health-related issues, and in some cases death.
Outlined are a series of steps to ensure best practice.
1 Take dung samples
To accurately determine the level of worms present in cattle, taking a few fresh dung samples from a group of cattle will give a good indication of when to dose.
It is also a good way of monitoring how effective your worm drench was at reducing worm levels. Talk to your vet about getting samples analysed.
2 Weigh cattle before dosing
Make sure you give cattle the required volume of your chosen worm drench to get maximum worm kill and residual cover.
Under-dosing makes the worm drench less effective, and increases the risk of immunity developing to a product.
If you cannot weigh cattle, group according to size and set the dosing gun for the heaviest animal in the group.
3 Dose cattle in a race, not a pen
Dosing cattle in a handling race will ensure that you can apply the worming product accurately. Some farmers using a pour-on product will opt to worm cattle in a holding pen.However, it is more difficult to apply, and there is increased safety risk for the operator.
4 Alternate worming products
Resistance to worming products is growing and, if you repeatedly use the same product every time you treat cattle, then cattle could potentially develop immunity.
Alternating worming products is highly recommended.
Use one type now and change to a different drench (with a different active ingredient) for a second treatment later this summer.
For instance, if using an avermectin-based product then you could use a levamisole-based product in late summer. Consult with your vet to draw up a worming programme for your herd.
5 Grazing management
Grazing management can also help improve worm control in cattle. Mixed grazing of cattle and sheep can help to reduce the worm burden on paddocks.
Using a leader-follower grazing system will provide clean grazing for young calves as they are always first into a paddock, with mature cows used to clean out paddocks.
Reseeded ground and silage aftermath will also provide clean grazing for young cattle or growing animals.
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