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Parasites Cause Problems In Beef Cow/Calf Herds

30 December 2009

US - In the last several years, we have been diagnosing more parasites in cattle. We are finding clinical problems in young calves at 300-400 pounds in the late summer. We are also seeing parasitised cows in early winter. A recent research paper on beef cow/calf anthelmintic research may help shed some light on the problem, says David Barz, DVM, Northwest Vet Supply.

Most producers (80 per cent) are using anthelmintic dewormers at least once per year on their cows. Only about six per cent of producers are utilising fecal testing to evaluate the efficiency of their programs. Most producers are merely using a pour-on product once yearly without any type of diagnostics to aid in their decisions.

Animals develop some immunity to internal parasites as they increase in age. Older cows tend to carry lower internal parasite populations than young animals (calves and yearlings). It is strange that the data shows only 70 per cent of operations deworm replacement heifers once yearly, 55 per cent deworm stockers and 53 per cent deworm preweaned calves. These young animals are the ones that really need to be wormed.

With years of usage, the pour-on dewormers have become less effective. The absorption of the topicals is quite variable and when low dosages and poor applications are added to the mix, parasites develop resistance to the lower doses. In recent years we are also seeing lice resistance to the old reliable pour-ons. Many producers are now pouring twice yearly to eliminate problems.

Most producers pour in the late fall and early winter for the lice populations. Deworming at this time is probably the least effective in reducing herd parasite populations. The parasite population explodes over the summer while the animals are on pasture. Some of these parasites then overwinter on the pasture. The best time to worm the cows is at turnout or shortly after. This avoids the increased populations through the summer and also minimizes calf exposure. If dewormer isn't doing a good job and producers use it at a poor time in the life cycle of the parasite, they are heavily infesting pastures with more and more parasite larvae.

Fecal egg count can give an assessment of both the type of parasites in the herd as well as the quantitative value of each parasite. This can be simply accomplished by collecting fresh fecal samples and sending them to a lab for examination. Several companies are doing these tests at no charge and will even pay the postage.

We now have many ways of deworming cattle. One practice is using drenches and injectables more intensely. Producers will inject at turnout and follow with a drench in August when working calves on the cow. Oral presentations can now be added to feeds and mineral. With careful planning dewormers can be used at important points of the parasites life cycle to minimise animal infestations and pasture contamination.

Using effective deworming products in a timely fashion is very important in limiting losses to parasites in cattle herds. Visit with a veterinarian or nutrition consultant. They will help sample the herd to evaluate parasite populations, devise a strategic and timely administration of appropriate products and resample the herd to measure the effectiveness of the programme used. A successful deworming programme will prevent pasture infestation while increasing animal performance.

TheCattleSite News Desk



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