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Worm and lice management in dairy cows

Worm and lice management in dairy cows

Worm and lice management in dairy cows

Targeted treatment of dairy cows in late lactation can help manage lice and worms in the herd.

All treatments must be given at the dose rate for the heaviest cow in the herd. If not, underdosing occurs, resulting in poor treatment outcomes where the parasites survive the sub-lethal doses. When this happens, it can breed resistance to the product. The heaviest cows may weigh from 100 to 200 kg more than the average, so weigh a sample of the herd to ensure the correct dose rate is delivered.

With recent changes in the milk withholding period (WHP) of some of the products used to treat cows for parasites and lice, it is important to read the product label before use.

Lice spend their entire life cycle on cows, laying eggs that stick to their coats. As lice cannot fly, they crawl to the end of the hair fibres to transfer to other cows. This occurs when the cows are held in close confinement such as in the yard. To help prevent the spread of lice, make sure the treatment spreads over the entire animal, by applying from the head to tail using a T bar applicator. Note, lice control is the only time the whole herd is treated and at the same time.

For an effective treatment to control lice on dairy cows, consider Vetmed’s Delmax® Pour On which has a nil milk WHP and a 28 day meat WHP.

For worm management, maintaining a population of worms in refugia from the drench is important as it slows the development of resistance. This can be achieved by leaving a portion of the cows untreated.¹ Adult cows in heavier body condition score (BCS) are good candidates to leave undrenched, while younger animals may benefit from a broad-spectrum drench.

Vetmed Epimax® Pour On contains the potent broad-spectrum endectocide eprinomectin with persistent activity for 14 to 28 days after treatment, depending on the worm species. With a nil WHP for milk, meat, and bobby calves, Epimax Pour On is ideal for use in late lactation.

In a situation where biting and sucking lice need to be controlled as well as treating and controlling intestinal worms, firstly determine which cows need a worm and lice treatment compared to those that only require a lice treatment.

For cows requiring only lice control, Vetmed’s Delmax Pour On is effective. For lactating cows needing treatment for worms and lice, Vetmed’s Moxidectin® Pour On contains the long-lasting broad-spectrum endectocide moxidectin, offering high efficacy against lice. The formulation has a nil milk, meat, and bobby calf WHP and has a registered claim to improve milk production. For cows at dry off, Vetmed’s Abamectin® Pour On is suitable and has a 35 day milk and meat WHP.

Visit your local PGG Wrightson store to discuss an effective worm and lice treatment and control programme for your dairy herd.

Written by Andrew Dowling on behalf of Agritrade

1 Wormwise. Worm Management. Retrieved from

Registered pursuant to the ACVM Act 1997, Vetmed Delmax Pour On #A011466, Vetmed Epimax® Pour On #A010922, Vetmed Moxidectin® Pour On #A010783 and Vetmed Abamectin® Pour On #A010786. Always read the registered label before use.