The worm challenge on every farm is different and changes every year and treatment plans should take into account unique factors such as farm location, disease history, current season/weather and the type and age of stock.

Wormers can be given to cattle via several different delivery methods, including drenches, injections, pour-ons and boluses. One of the key attributes when selecting wormers, and which has a direct impact on how they should be used, is their persistent activity.

Short-acting: duration of activity one day only – Any of the products containing a BZ or LV other than boluses – All the flukicides singly or in combination products.

Long-acting: duration of activity typically around four weeks, depending on worm species – ML injections and pour-ons – Combination products containing MLs

Ultra-long-acting: duration of activity four to five months – BZ boluses – ML (moxidectin) long-acting injection

The advantage of long-acting products is that they require less frequent administration and therefore less animal handling.

The ultra-long-acting products effectively provide cover for a complete grazing season. A potential disadvantage of persistent activity is that it may accelerate selection for anthelmintic resistance compared with short-acting products. Although there is currently no scientific evidence that this occurs in cattle.

Youngstock first grazing season

The risk posed by worms to youngstock depends on when they were born and whether they are grazing with their mothers or have been weaned.

The most susceptible are weaned calves grazing for the first time on pastures that have carried cattle any time in the preceding 12 months, as they have no immunity and rely solely on grass for food.  Autumn-born suckler calves can be quite susceptible, but benefit from their mothers’ milk, which reduces reliance on the pasture alone and provides some protection from the effects of worms too.

Spring born calves are the least at risk, as grass and therefore worm larvae, comprise a relatively small proportion of their intake until they are weaned in autumn.

For example:

First Grazer Boluses – For use in grazing cattle 100-400kg, their first grazing season. The device will deliver seven doses of oxfendazole for the treatment of both adult and immature gastro-intestinal roundworms, lungworms and tapeworms at regular intervals of approximately three weeks during a period of approximately 21 weeks

 Youngstock second grazing season

Several important production targets can occur during the second grazing season, e.g. mating of replacement heifers and finishing of nonbreeding stock. The most important potential impact of parasites in these animals is on their growth rates, as any reductions in live weight gain will delay service or marketing.

Consequently, the best indicator for parasite control or treatment is live weight gain, which is a good indicator of parasite burden, providing the feed is adequate and that there are no other obvious causes of poor growth.

For example:

Finisher Boluses – Used for grazing cattle weighing between 100-400 kg at the time the bolus is given. Designed for dosing prior to turnout of cattle in their second grazing season. The device will deliver five doses of oxfendazole for the treatment of both adult and immature gastro-intestinal roundworms, lungworms and tapeworms at regular intervals of approximately three weeks during a period of approximately fifteen weeks.

On farms which are at high risk for fluke, this parasite will need to be controlled in yearlings.

Adult cattle

Adult cows are generally immune to gut worms and lungworms if they have had adequate exposure. However, under some circumstances, ill-thrift and even clinical disease can occur.

Nevertheless, beef cows do not normally need to be treated routinely, though worming at housing can be a useful, low-risk option to keep gut and lungworm populations down.

There is no immunity to liver fluke, so if cows graze high fluke pastures, they will need treating at least once a year, typically at housing and possibly once again during the grazing season.

Do not forget breeding bulls, they are more susceptible to worms than cows, so may benefit from worming, particularly leading up to the breeding season.

Options for older cattle dependent on risk and exposure – Pour On Ivermectin or Long Acting Injection

Liver fluke

Yearling and adult cattle should be treated after housing. Dependent on active ingredient used – triclabendazole should be administered a week after housing. Closantel should be administered 8 weeks. Products vary in their ability to kill juvenile fluke and the timing of administration may need to be adjusted accordingly. Animals kept outdoors may require additional treatments, depending on the liver fluke risk.

Given the resistance issues emerging with the flukicide triclabendazole, it is important to limit use of this product. And alternative products can be used for treating adult liver fluke in cattle like closantel and nitroxynil.

NB: Keeping stock off wet areas which could harbour the mud snail intermediate host will help reduce incidence of disease.


Determine which parasites are already on the farm and which ones need to be kept out. If possible, speak to the vendor to see what parasites may be present and what treatments have been given before sale.

If it is practical, yard or house all purchased cattle and administer an appropriate anthelmintic for the target parasites. This may include a combination of different anthelmintics, administered sequentially, targeting different worms including ML-resistant Cooperia.

Dung samples can be taken two to three weeks after treatment to establish if the treatments have been successful in removing all the parasites. If worm counts are negative, then cattle can be turned out if desired.

For more advice on individual plans ring Sally Cornforth on 01765 680216

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