Emergency Treatment of Lice in Spring
/Cows with heavy lice infestation are up to 10% less productive due to eating less, because they are distracted or itching.
Lice are the most important winter parasite of cattle; you will see a lot of scratching and hair loss over the neck and shoulder. I strongly believe that severe lice infestations do cause milk production and BCS loss in dairy cattle. Furthermore, lice burdens are often highest in cattle which are in poor condition and have been tight for feed over the winter.
While it would have always been better to have treated cattle for lice in early winter a salvage treatment can still be used in the spring. The critical thing is to dose all cattle with an effective dose and product.
Product choice becomes vitally important as we head into spring due to both the milk and bobby calf with holds.
Pour on “Mectin” treatment options- These treat both lice and internal parasites:
Cydectin is the logical choice in this situation as it achieves good control of both lice and internal parasites. It has the advantage of both a nil milk and meat withhold. The bobby calf meat withhold is also nil.
While pour-on drenches containing Abamectin are great options for controlling lice MPI implemented a new milk and meat with holding time of 35 days in Sept 2022. This means Reflex and Topline are largely restricted to being used as dry off treatments in the autumn.
Pour on lice only treatment options:
Blaze is a synthetic pyrethroid pour-on which has a nil milk withhold and 28-day meat withhold. There is no bobby calf withholding period.
Destruct is a pour-on organophosphate which has a 3-day meat withhold and 5-day milk withhold.
It is important to be aware that when any of these pour on products are applied to cattle that have come straight off crop and have thick coats covered in mud or faeces, then efficacy may be compromised. Lice numbers will rebuild again over 8 weeks, often requiring another treatment.
