August 27, 2014
As the daylight hours begin to decrease, cattle’s hair coats grow longer and thicker in preparation for colder temperatures and winter weather. It really is quite amazing how much protection is provided to the animal by its hair coat.
But the cow isn’t the only critter that can benefit from the protection afforded in this case. Lice are just waiting for their chance, and a long, thick hair coat is just what they need.
Probably the biggest challenge in controlling lice is an understanding of the types of lice that may infest your cattle. For our purposes, there are several different species of lice, but they fall into two general types — biting and sucking lice. The distinction is important, as understanding how the two types of lice acquire their nutrients is a primary key to controlling them.
Biting lice (Bovicola bovis) survive by feeding on the skin, hair and sloughed skin cells of the animal. A complete life cycle of this louse can occur in as little as three weeks, and adults can live as long as 10 weeks.
Meanwhile, sucking lice survive by penetrating the skin and feeding on blood. The species of sucking lice include: the longnosed cattle louse (Linognathus vitulii), the little blue cattle louse (Solenopotes capullati) and the shortnosed cattle louse (Haematopinus eurysternus).
Both biting and sucking lice are spread by direct contact, and are typically found along the animal’s topline, particularly around the withers.
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Cows are commonly treated for lice at the time of pregnancy examination. It’s also common practice to forego vaccinating and treating open cows for lice, as they will most likely be culled. If this is done, make sure that the untreated cows are kept separate from the treated cows, as the untreated cows can be a source of re-infestation for the treated cows.
This caution should also be kept in mind when cows are purchased as replacements, as these cows could also be a source for lice re-infestation for the rest of the herd. Bulls, too, should be treated, as this will help keep them in good shape for the next breeding season. Plus, should untreated bulls happen to get mixed in with the cows during the winter, they could serve as yet another source for re-infesting the rest of the herd with lice.
One of the first and most obvious signs of significant lice infestation is hair loss, especially on the cattle’s shoulders and back. Rubbing on fences is another, as is cattle swinging their heads while trying to flick their tongues to their withers. Sometimes, the whipping of the tongue can hit the back so hard that a slapping sound can be heard.
In the feedyard, rubbing and scratching can result in the destruction of fences, but also carcass bruising and other injuries. And severe infestations can result in anemia, abortions and impaired immune response.
If lice have a good attribute, it’s that their entire life cycle occurs on the animal. This allows for effective control because we know where the target is. Of course, lice can leave the animal, but they’ll survive only a few days without nourishment.
A multitude of products are available for lice control, including pour-ons, dusts, sprays and injectable products. Most are very effective.
The avermectin pour-on products provide good control of both biting and sucking lice, but may not provide good deworming efficacy. Meanwhile, the injectable avermectin products provide good control of sucking lice, but very poor control of biting lice. Thus, if an avermectin injectable is used for deworming, lice control won’t be very good unless another product is used in conjunction with it.
As always, the best advice is to consult with your herd health veterinarian to determine which products will be most effective for the types of lice and time of year.
Dave Sjeklocha, DVM, is director of animal health for Cattle Empire, LLC, of Satanta, KS. He can be reached at [email protected].
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