Lice eat into profits

Lice is a common external parasite in dairy cattle, most notably detected by visible loss of hair. Infestations occur predominantly in the winter months from December through March when cattle have thick winter hair coats. This is compounded by having seasonally less light and the tendency for animals to crowd or bunch together.
Lice infestations are more than a cosmetic issue. Cattle lice infections can affect the health and performance of animals during with winter months. The U.S. Department of Agriculture has estimated that livestock producers lose up to $125 million per year due to effects of lice infestations.
Lice are small, flat-bodied insects with legs modified for grasping hairs. Cattle serve as the host to lice and are critical to their survival. Lice can only live away from the animal for a few days. Two common species of lice that infest cattle are biting lice and sucking lice. Biting lice eat skin debris and secretions on the outside of the animal while sucking lice pierce the skin with their narrow, pointed heads and suck blood from the host. Lice are species-specific, suggesting cattle lice cannot affect people or other livestock species.
Female lice will lay an egg at the base of cattle hair follicles, and the eggs are essentially glued individually to the hair. It takes about two weeks for the baby lice, or nymphs, to hatch. The nymphs resemble adult lice but are smaller. It takes them about three weeks to mature to adult lice. The adult lice live for about two to three weeks and, as reported by University of Kentucky entomologists, the females lay about one egg per day.
Determining the severity of the infestation is the first step in developing an action plan against lice infestation. One method is to count and record the number and species of lice found per square inch of the hide. Biting lice will move when disturbed and are usually not found clustered with other lice, so you will see individual lice jumping around. In contrast, sucking lice will tend to stay stationary when disturbed and like to group together. Kentucky specialists have referenced 10 lice per square inch as the economic threshold for treatment initiation. However, producers will often treat with any presence of lice to proactively prevent reinfestation and, in some cases, just for the improved appearance that results.
The most common sign that cattle are suffering from a severe lice infestation is hair loss and raw spots, leading to increased maintenance costs associated with additional energy to keep animals warm in the winter. This is often combined with reduced weight gain, health and general thriftiness. Studies have shown average daily gain of growing calves reduced by up to 0.25 pounds per day, resulting in decreased feed efficiency. Lice infestations can also lead to skin infections, potential blood loss and anemia in severe cases, and wear and tear on facilities and fences.
Lice populations will decrease in activity as the weather starts to warm. This may influence the decision to treat, especially in cases where lice numbers are low or animals do not seem bothered by the lice infestation.
When treating cattle, it is important to treat the entire group. Missing even one animal could allow it to serve as a reservoir for reinfesting the entire herd. A variety of products are available for control of lice. If you decide to treat a lice infestation, select a product that will work the best for the population of lice you have present. Biting lice are most effectively treated with a topical treatment. Sucking lice feed on blood and serum, so they are controlled more effectively with a systemic injectable product. To achieve a more complete kill, as second treatment may be necessary to capture those lice that were in the egg and infancy stage during the initial treatment.
Work with your veterinarian and herd health advisors to determine which products fit the needs of your dairy. Implementing an effective lice control program will allow your herd to maintain optimal health status and maximize performance.
    Barry Visser is a nutritionist for Vita Plus.


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