Dave Barz, DVM

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December 2, 2011
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Vet's Voice: Internal parasite control methods

Thanksgiving has given cattle producers many reasons to be thankful. Feeder calf and fat cattle prices are at high levels and now corn prices are sliding. Now is an ideal time to administer internal parasite control to gain added performance benefits.

Research has shown that parasites cost the beef industry over $3 billion annually in lost weight gains, poor feed conversion and increased disease. Most producers dewormed and vaccinated calves earlier in the fall. Parasite-inflicted calves respond poorly to vaccination because they mount a poor immune response. High calf prices and high feed prices greatly magnify the return benefit of parasite control. Several extra pounds at market or slaughter will more than pay for the entire parasite control program.

In our area we are pregnancy-checking and vaccinating cowherds. This is a great time to administer a parasite prevention program. For the past 10 years most producers have used a pour-on avermectin for control. These topical applications must be absorbed to be effective against internal parasites. In the past, low doses of these products were administered, with only fractional levels being absorbed, contributing to parasites developing resistance to avermectin pour-ons. Even lice are becoming resistant.

There are many effective broad-spectrum products on the market. There are times when not any one single parasiticide treatment will control all parasites perfectly. If a producer has been using a single product for several years, it may be a good time to rotate to another product.

We commonly use oral wormers when pregnancy-checking because the cow is restrained in a chute. These products are hard to administer, but work well on most internal parasites. The weakness of drenches is the inability to effectively control inhibited Ostertagagia ostertagi. This is one of the most damaging internal parasites which persist in the animal for indefinite periods as an inhibited larval form. The larvae mature sometime later and become parasitic adults. Oral-administered products also have no control of external parasites.

Injectable avermectins are excellent against the inhibited Ostertagia and most external parasites. These products are poorly effective on biting lice in the area. We usually use injectable avermectins at calf turnout and again with the first round of pasture vaccinations. We believe we get some additional late-season fly control from the products. At weaning we will give an oral product and a pour-on for lice.

Within the cow, it is possible to effectively mix products and methods of administration. Oral dewormers can be used effectively within feed at any time during gestation or lactation. Many clients agree with deworming; they believe they gain a body condition score, or about 100 pounds, from effective parasite control. The cows stay in better condition, produce healthier calves and produce quality colostrum. Once a client starts a deworming program they stay with it because they can visually see the results.

There are no products that are completely effective against all internal and external parasites. Poor decisions and timing surrounding appropriate parasite control product selection can end up costing much more in the long run. Consult a veterinarian, nutritionist, or extension specialist to determine the parasite population affecting your herd's profits. Devise a cost effective program using a combination of products to garner all the benefits for every dollar spent while synchronizing applications with normal passage of cows through the chute. This will generate additional dollars for the cow-calf feeding operation.

Thanksgiving has given cattle producers many reasons to be thankful. Feeder calf and fat cattle prices are at high levels and now corn prices are sliding. Now is an ideal time to administer internal parasite control to gain added performance benefits.

Research has shown that parasites cost the beef industry over $3 billion annually in lost weight gains, poor feed conversion and increased disease. Most producers dewormed and vaccinated calves earlier in the fall. Parasite-inflicted calves respond poorly to vaccination because they mount a poor immune response. High calf prices and high feed prices greatly magnify the return benefit of parasite control. Several extra pounds at market or slaughter will more than pay for the entire parasite control program.

In our area we are pregnancy-checking and vaccinating cowherds. This is a great time to administer a parasite prevention program. For the past 10 years most producers have used a pour-on avermectin for control. These topical applications must be absorbed to be effective against internal parasites. In the past, low doses of these products were administered, with only fractional levels being absorbed, contributing to parasites developing resistance to avermectin pour-ons. Even lice are becoming resistant.

There are many effective broad-spectrum products on the market. There are times when not any one single parasiticide treatment will control all parasites perfectly. If a producer has been using a single product for several years, it may be a good time to rotate to another product.

We commonly use oral wormers when pregnancy-checking because the cow is restrained in a chute. These products are hard to administer, but work well on most internal parasites. The weakness of drenches is the inability to effectively control inhibited Ostertagagia ostertagi. This is one of the most damaging internal parasites which persist in the animal for indefinite periods as an inhibited larval form. The larvae mature sometime later and become parasitic adults. Oral-administered products also have no control of external parasites.

Injectable avermectins are excellent against the inhibited Ostertagia and most external parasites. These products are poorly effective on biting lice in the area. We usually use injectable avermectins at calf turnout and again with the first round of pasture vaccinations. We believe we get some additional late-season fly control from the products. At weaning we will give an oral product and a pour-on for lice.

Within the cow, it is possible to effectively mix products and methods of administration. Oral dewormers can be used effectively within feed at any time during gestation or lactation. Many clients agree with deworming; they believe they gain a body condition score, or about 100 pounds, from effective parasite control. The cows stay in better condition, produce healthier calves and produce quality colostrum. Once a client starts a deworming program they stay with it because they can visually see the results.

There are no products that are completely effective against all internal and external parasites. Poor decisions and timing surrounding appropriate parasite control product selection can end up costing much more in the long run. Consult a veterinarian, nutritionist, or extension specialist to determine the parasite population affecting your herd's profits. Devise a cost effective program using a combination of products to garner all the benefits for every dollar spent while synchronizing applications with normal passage of cows through the chute. This will generate additional dollars for the cow-calf feeding operation.


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Tri-State Livestock News Updated Aug 14, 2012 04:07PM Published Dec 2, 2011 10:32AM Copyright 2011 Tri-State Livestock News. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.