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Decoding dewormers

Dave Barz, DVM
For the Jan. 2, 2010 edition of Tri-State Livestock News.

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Christmas has quickly come and gone. After the weeks of preparation it was greatly simplified by a monster blizzard. I hope all of you had a Merry Christmas and were able to celebrate with your families. Now we must look forward to 2010, hopefully a better year for the livestock producer.

In the last several years we have been diagnosing more parasitizms in cattle. We are finding clinical problems in young calves at 300-400 pounds in the late summer. We are also seeing heavily parasitized cows in the early winter. A recent research paper on beef cow-calf anthelminic research may help shed some light on the problem.

Most producers (80 percent) are using anthelmentic dewormers at least one per year on their cows. Strangely only about six percent of the producers are utilizing 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 the increase in age. Older cows tend to carry a lower internal parasite populations than young animals (calves and yearlings). It is strange that the data shows only 70 percent of operations deworm their replacement heifers once yearly, 55 percent deworm stockers, and only 53 percent deworm preweaned calves. These young animals are the ones which 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 doseages 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 of you are now pouring twice yearly to eliminate problems.

Most of us 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 parasites population explodes over the summer while the animals are on pasture. Some of these parasites then overwinter on the pasture. Our 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 our dewormer isn’t doing a good job and we use it at a poor time in the life cycle of the parasite, we are heavily infesting our pastures with more and more parasite larvae.

Fecal egg count can give you an assessment of both the type of parasites in your herd as well as the quantative 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. What do you have to lose versus what you will gain?

We now have many ways of deworming our cattle. Our practice has been using drenches and injectables more in intensely. We will inject at turnout and follow with a drench in August when we work 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 minimize animal infestations and pasture contamination.

Using effective deworming products in a timely fashion are very important in limiting losses to parasites in our cattle herds. Visit with your veterinarian or nutritional consultant about your operation. They will help you sample your herd to evaluate your parasite populations, devise a strategic and timely administration of appropriate products and resample your herd to measure the effectiveness of the program you used. A successful deworming program will prevent the infestation of your pasture while increasing the performance of your animals and conserving your feedstuffs. This will add dollars to your bottom line.

Christmas has quickly come and gone. After the weeks of preparation it was greatly simplified by a monster blizzard. I hope all of you had a Merry Christmas and were able to celebrate with your families. Now we must look forward to 2010, hopefully a better year for the livestock producer.

In the last several years we have been diagnosing more parasitizms in cattle. We are finding clinical problems in young calves at 300-400 pounds in the late summer. We are also seeing heavily parasitized cows in the early winter. A recent research paper on beef cow-calf anthelminic research may help shed some light on the problem.

Most producers (80 percent) are using anthelmentic dewormers at least one per year on their cows. Strangely only about six percent of the producers are utilizing 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 the increase in age. Older cows tend to carry a lower internal parasite populations than young animals (calves and yearlings). It is strange that the data shows only 70 percent of operations deworm their replacement heifers once yearly, 55 percent deworm stockers, and only 53 percent deworm preweaned calves. These young animals are the ones which 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 doseages 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 of you are now pouring twice yearly to eliminate problems.

Most of us 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 parasites population explodes over the summer while the animals are on pasture. Some of these parasites then overwinter on the pasture. Our 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 our dewormer isn’t doing a good job and we use it at a poor time in the life cycle of the parasite, we are heavily infesting our pastures with more and more parasite larvae.

Fecal egg count can give you an assessment of both the type of parasites in your herd as well as the quantative 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. What do you have to lose versus what you will gain?

We now have many ways of deworming our cattle. Our practice has been using drenches and injectables more in intensely. We will inject at turnout and follow with a drench in August when we work 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 minimize animal infestations and pasture contamination.

Using effective deworming products in a timely fashion are very important in limiting losses to parasites in our cattle herds. Visit with your veterinarian or nutritional consultant about your operation. They will help you sample your herd to evaluate your parasite populations, devise a strategic and timely administration of appropriate products and resample your herd to measure the effectiveness of the program you used. A successful deworming program will prevent the infestation of your pasture while increasing the performance of your animals and conserving your feedstuffs. This will add dollars to your bottom line.


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