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Worms at grass across the summer months;
In young stock, severe infection can reduce growth rates by up to 30%
Immunity at turnout:
1st year grazing = no immunity, dose when symptoms appear
2nd year grazing = some immunity, dose if symptoms appear, may require 1 dose
3rd year + grazing (Adult cows) = good immunity (unless immuno challenged or poor nutrition), dose if symptoms appear
Do I need to dose?
Calves should be left at least three weeks after turnout to build up natural immunity against gut worms, but ideally calves should only be treated for the first time when symptoms show. Take dung samples and monitor egg counts monthly.
What are the symptoms of stomach worms?
What are the symptoms of lung worms?
Lungworm is diagnosed when cattle start coughing up the worms- this is an emergency and needs immediate dosing.
Reducing the risk:
Control of gut worms;
An effective control strategy should control the worm burden while allowing the calve to build up its natural immunity.
There are currently 3 classes of wormers licenced in Ireland;
These kill the worm on the day but offer no residual effect. White wormers come as oral doses and in a bolus.
Repidose is a white wormer that offers season long control from handling the calves once while also allowing the calves natural immunity to develop.
These kill the worm on the day but offer no residual effect. These are available as injectables, pour-ons and oral doses.
These products will kill worms on the day of dosing and for the following 2 weeks. Therefore, you would need to dose every 5 weeks with these products (3-8-13 weeks).
These products are available as injectable and pour-ons. Cydectin LA is a macrocyclic lactone that offers 18 weeks of continuous cover from time of dosing, but it will not allow the calves natural immunity to develop, until the end of the season.
The genes responsible for anthelmintic resistance are believed to be present in all worm
populations but at very low levels. When animals are treated with an anthelmintic, this kills all the susceptible worms allowing only the resistant worms to survive.
The surviving resistant worms output eggs with the dung onto pasture which results in resistant worms making up a much greater proportion of the worm population in subsequent generations.
A 2017 Teagasc survey found:
How to avoid resistance
Gut worms in milking cows:
Bulk Milk testing for Ostertagia will identify if there is a problem with worms in the herd, However, recommendations for dosing should be done in conjunction with a dung sample.
If the Ostertagia result in milk are over 0.7, there will be value in treating the younger cows in the herd for worms. If the result is higher than 1.0, all cows
will benefit from treatment due to an increased worm burden from the grass. If your only treat a section of your stock (i.e 1st calver) do not use a pour-on, as untreated animals
can lick the dose from the treated animal back, leading to partial dosing and worm resistance. If you’re only treating the 1st calvers use an injectable.
Lung Worm in milking cows:
Diagnosis of lungworm in the herd is not as simple as for Ostertagia. Stomach worms build up slowly leading to increasing egg counts and milk levels.
Lungworm explodes into a full-blown outbreak in a few days. Cows will also start coughing before they start shedding eggs in their dung.
For farms where there is a known risk of lungworm, treatment should be used once a few cows begin to cough. All cows in the herd should be treated for lungworm as the infection will have been picked up by all animals when grazing
Only Eprinomectin products have zero milk withhold in lactating animals.
NOTE: When treating cows for lungworm, even though the product will work quickly, animals may continue to cough for a period of time until all of the dead worms have been cleared from the lungs