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External Parasites: If It's Not One Thing, It's Another
Just when the flies back off, and you think you can take a break from parasite control, what turns up? Lice. The bane of the year's cooler months, lice appear in greatest numbers in the late fall, winter, and early spring. During spring and summer, the skin temperature of cattle may go well over 100° F, which is warmer than lice can tolerate for producing eggs.
Get to Know Lice
Two types of lice infest cattle: sucking and biting or chewing. Within those types, there are four species of sucking lice and two species of biting or chewing lice. While cattle lice have preferences for particular breeds and ages of cattle, all follow similar patterns. They are typically found in the folds of the skin around the area of the head, neck, withers, and the inner surfaces of the legs. Chewing lice feed on the skin while sucking lice pierce the skin and feed on the animal's blood. Both types create intense irritation that causes animals to rub, lick, and bite infested areas. An easy tip-off to lice problems is cattle with a rag-tag appearance and frequent rubbing.
The life cycle of all species of lice are also similar. All cattle lice are obligate parasites. That is, they must remain on the host to survive. If eggs or lice fall off with shedding hair, they survive only a few days.
Lice attach their eggs (nits) to the hair of the host, close to the skin. In one to two weeks, nymphs hatch and begin to feed, grow and in two to three weeks reach maturity. The mature adults mate, and the females attach their eggs to the hair of the host. This period from generation to generation varies in length from 20 to 31 days. Their relatively short life cycle and the fact that a mature female lays between 30 to 50 eggs accounts for the rapid increase in lice infestation during the louse season.
What Lice Do to Your Bottom Line
Cattle lice are small, but they can bite into your herd's profits. Even moderate infestations cause calves and feeders to grow at slower rates and consume more feed per pound of gain. In University studies, lice infestations have shown to decrease average daily gains in various types of cattle by up to 9.2%.1
Lice damage doesn't stop with reduced performance. Infested cows produce less milk for their calves. Blood loss caused by sucking lice can become so severe it causes anemia which, in turn, can lead to abortion in young heifers. Extreme infestations can result in death.
In addition, cattle infested with lice often damage fences as well as hurt themselves as they rub to relieve the itching caused by the lice on their bodies.
Annual production losses in cattle due to lice adds up to more than $126.3 million, according to USDA estimates.2
Control Options That Work
Untreated lice populations peak in late winter when cattle are also stressed from cold weather and possible vitamin A deficiencies. Levels decline rapidly with spring warm-up, but some animals in the herd, such as bulls, can become year-around hosts for this parasite.
Treat for lice early in the winter before infestations can cause serious damage to cattle. Because of their short life cycle and the fact that treating eggs is not effective, repeating treatments may be necessary for optimal control. Consider applying a pour-on insecticide during cold weather. Insecticides in dust bags and backrubbers can also help to keep lice infestations from reaching severe levels.
Schering-Plough Animal Health offers a number of pour-on options to help you control lice. The one you select will depend on your lice problems and type of herd. The recommended choice for beef cattle is SaberTM, while for dairy cattle-both lactating and non-lactating-the recommended choices are Boss® and Ultra BossTM.
- Saber is a fast-acting, long-lasting formulation of Schering-Plough Animal Health's proprietary insecticide lambdacyhalothrin. It is effective at very low dosage rates, and only two dose volumes need to be calculated based on whether cattle weigh more or less than 600 pounds. Saber has no preslaughter withdrawal and is approved for beef cattle of all ages (excluding veal calves).
- Boss is a scientifically developed formula of 5% permethrin in low-volume dosage, which reduces labor. Boss provides 90% efficacy for up to five weeks and residual control for up to seven weeks.3 It requires no preslaugher withdrawal and no milk discard, and it is approved for all classes of beef cattle, dairy cattle, and sheep.
- Ultra Boss is a fast-acting, long-lasting formulation of both 5% permethrin and 5% piperonyl butoxide, for optimizing lice control. The powerful activity of Ultra Boss reduces the need for frequent retreatment. Like Boss, it requires no preslaughter withdrawal and no milk discard, and it is approved for all classes of beef cattle, dairy cattle, and sheep.
Remember that lice are a problem in the fall and winter, when other external parasites are usually inactive. So, select control products that are lice-specific and don't waste money with internal/external products that aren't needed at this time of year. Begin your treatment program early and monitor animals monthly to catch and treat any reinfestations that may occur. Your cattle will be able to perform better, and so will your bottom line.
1"The Economic Impact of Parasitism in Cattle," edited by William H.D. Leaning, BVSc, and Jorge Guerrero, DVM, PhD, Table 10, page 20, August 1987.
2From "A Review of Ectoparasites and Their Effect on Cattle Production" as presented at a symposium titled Parasites Affecting Forage Livestock Research at the Southern Section ASAS Annual Meeting, 1991.
3Data on file at Schering-Plough Animal Health Corp.
©2001 Schering-Plough Animal Health Corp. All rights reserved. Ultra Boss and Saber are trademarks, and Boss is a registered trademark of Schering-Plough Veterinary Corp.
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