Why Parasite Control Matters
Gastrointestinal parasites (helminths) reduce nutrient absorption, impacting milk production and growth. Managing these parasites through pasture management and targeted deworming supports healthier, more productive dairy herds.
Who Needs Deworming?
Young and high-producing grazing cows benefit most. First and second lactation cows may need treatment around calving. Older cows (third lactation and up) often don’t require deworming if they maintain good body condition. Use fecal egg counts (FEC) and body condition scores (BCS) to decide.
Cattle in dry lots are typically parasite-free. However, newly purchased animals should be tested and treated if needed. Use fecal egg count reduction (FECR) tests to confirm treatment success.
Why Not Deworm Everyone?
Some animals should remain untreated to maintain refugia—a population of parasites still susceptible to dewormers. This helps prevent resistance by maintaining a mixed parasite gene pool.
Strategic Deworming
Deworming in fall lowers parasite levels before winter. In spring, treat before pasture turnout to reduce contamination. For grazing youngstock, use the “0-4-8” rule—deworm at turnout, then at four and eight weeks. Avoid deworming lightweight, suckling calves; treat only around weaning if needed.
Use FEC to Guide Decisions
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Fall/Winter FEC: Reflects last grazing season. High counts may require treatment.
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Spring FEC: Time testing with temperature rise and before turnout.
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Summer FEC: Confirms treatment success or highlights reinfection.
Sample 20% of the herd (or 20 animals) before treatment and retest the same animals two weeks later. A 90% reductionconfirms product effectiveness.
Correct Dewormer Use
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Follow label instructions carefully.
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Dose accurately—based on weight.
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Injectables and drenches are most reliable.
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Pour-ons and feed-throughs require proper administration and uniform access.
Bottom Line
Effective parasite control in dairy cattle means using lab tests, monitoring cow condition, and applying strategic treatments. This approach protects herd health, supports milk production, and helps preserve dewormer effectiveness long term.
