Cow Tales column: Parasite control for cattle | TSLN.com
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Cow Tales column: Parasite control for cattle

Kenny Barrett Jr., DVM, MS
For the September 18, 2010 edition of Tri-State Livestock News.

The tri-state area has experienced a wonderful summer. Most producers have received timely rains and managed to roll up a bumper hay crop.

Fall is fast approaching and the nighttime lows continue to dip lower. It is hard to travel very far through the countryside without coming across a fall gather. Ranchers are busy administering preweaning vaccinations.

Many cows have begun enduring the annual veterinary special. The yearly brown-arm event is the culmination of the events from the last year deciding who stays and who goes. It is a great time to monitor body condition, identify and cull poor performers, administer some biologics, and strategically treat for parasite infestation.

There are many parasites that infest cattle including intestinal worms, stomach worms, lung worms, grubs, sucking lice, biting lice, tapeworms, coccidia and others. There are nearly as many antiparasitics for producers to choose from.

Internal parasites destroy healthy tissue leaving it scarred and less effective. Ostertagia, the stomach worm of cows, can destroy the gastric glands of the stomach; leaving the lining with a Moroccan leather appearance that is ineffective at digestion.

Many internal worms have a developmental phase that includes larvae migrating through the lung tissue causing permanent damage. By feeding on body tissue or fluids and damaging digestive tissues, internal parasites decrease the animals’ ability to perform optimally and can even lead to death.

Internal parasites are basically spread by fecal-oral transmission; meaning cows consume forage contaminated with parasite larvae. Parasites are vulnerable to drying and extreme temperatures. To take advantage of this, it is best to administer fall antiparasitics as close to or after the fall freeze. This should prevent treated animals from becoming reinfested.

However, it is important to note coccidia require different control and treatment strategies when compared to the other parasites. Producers need to watch for signs of scours, especially bloody or dark scours, in younger animals around times of stress. Coccidiosis can be relatively easy to treat with quick intervention.

With fly season almost at an end we are mostly concerned with internal parasites and lice, eliminating insecticides from the discussion. Generally speaking, producers can choose from three basic products; pour-ons, injectables and drenches. They are not all equal in terms of efficacy or duration of effect.

Many studies would suggest the drenches, or white dewormers, which are administered orally, are the most effective at reducing the internal worm burden followed by the injectable products and lastly the pour-on parasiticides.

However, the drenches have no effect on lice. The creepy crawlies are sure to surface in mid- to late-winter without concurrent treatment with an injectable or pour-on product. Mid-winter lice problems such as these can be hard on fences, corrals and facilities. Extreme infestations of sucking lice can kill individual animals. Though the pour-on and injectable dewormers are less effective at controlling internal worms, they generally have the best activity against lice. Choosing the product with the greatest return on investment is the key.

Fecal egg counts are one tool producers can utilize to guide themselves and their veterinarians through the dewormer selection process. Knowing the level of parasitism before treatment can impact the product chosen. Eliminating ninety percent of ten worms is less important than removing ninety percent of two hundred worms.

Fecal egg counts are a measure of the number of parasite eggs in a specific amount of feces. The eggs produced by internal worms are concentrated in the laboratory to be counted under a microscope. However, there can be considerable variation from one sample to another. For the best results producers need to obtain twenty “grab samples” from a group of cows to accurately estimate the parasite burden.

A grab sample can be obtained riding through the pasture and observing the deposition of fresh samples. Simply invert a “zipper” style plastic bag over the sample and collect a small amount. Our current recommendation is to sample replacement heifers/yearlings and the mature cow herd separately. Younger animals have not developed the same level of immunity to parasites and can be more severely affected. It may provide a greater return to treat these two groups of animals differently.

The days of Warbex are over and parasite control in cattle is more complicated than splashing some blue tinted liquid over the cow as she runs past. Some cows, even in a relatively small geographical area, can have large parasite problems while neighboring herds are affected very little.

Parasites reduce growth, reproduction and hamper the immune system. Strategic control of parasites should return a net gain when administered timely and relative to a given parasite problem. Strategic control of parasites includes measuring current parasite infestations and working with your veterinarian to formulate effective control.

The tri-state area has experienced a wonderful summer. Most producers have received timely rains and managed to roll up a bumper hay crop.

Fall is fast approaching and the nighttime lows continue to dip lower. It is hard to travel very far through the countryside without coming across a fall gather. Ranchers are busy administering preweaning vaccinations.

Many cows have begun enduring the annual veterinary special. The yearly brown-arm event is the culmination of the events from the last year deciding who stays and who goes. It is a great time to monitor body condition, identify and cull poor performers, administer some biologics, and strategically treat for parasite infestation.

There are many parasites that infest cattle including intestinal worms, stomach worms, lung worms, grubs, sucking lice, biting lice, tapeworms, coccidia and others. There are nearly as many antiparasitics for producers to choose from.

Internal parasites destroy healthy tissue leaving it scarred and less effective. Ostertagia, the stomach worm of cows, can destroy the gastric glands of the stomach; leaving the lining with a Moroccan leather appearance that is ineffective at digestion.

Many internal worms have a developmental phase that includes larvae migrating through the lung tissue causing permanent damage. By feeding on body tissue or fluids and damaging digestive tissues, internal parasites decrease the animals’ ability to perform optimally and can even lead to death.

Internal parasites are basically spread by fecal-oral transmission; meaning cows consume forage contaminated with parasite larvae. Parasites are vulnerable to drying and extreme temperatures. To take advantage of this, it is best to administer fall antiparasitics as close to or after the fall freeze. This should prevent treated animals from becoming reinfested.

However, it is important to note coccidia require different control and treatment strategies when compared to the other parasites. Producers need to watch for signs of scours, especially bloody or dark scours, in younger animals around times of stress. Coccidiosis can be relatively easy to treat with quick intervention.

With fly season almost at an end we are mostly concerned with internal parasites and lice, eliminating insecticides from the discussion. Generally speaking, producers can choose from three basic products; pour-ons, injectables and drenches. They are not all equal in terms of efficacy or duration of effect.

Many studies would suggest the drenches, or white dewormers, which are administered orally, are the most effective at reducing the internal worm burden followed by the injectable products and lastly the pour-on parasiticides.

However, the drenches have no effect on lice. The creepy crawlies are sure to surface in mid- to late-winter without concurrent treatment with an injectable or pour-on product. Mid-winter lice problems such as these can be hard on fences, corrals and facilities. Extreme infestations of sucking lice can kill individual animals. Though the pour-on and injectable dewormers are less effective at controlling internal worms, they generally have the best activity against lice. Choosing the product with the greatest return on investment is the key.

Fecal egg counts are one tool producers can utilize to guide themselves and their veterinarians through the dewormer selection process. Knowing the level of parasitism before treatment can impact the product chosen. Eliminating ninety percent of ten worms is less important than removing ninety percent of two hundred worms.

Fecal egg counts are a measure of the number of parasite eggs in a specific amount of feces. The eggs produced by internal worms are concentrated in the laboratory to be counted under a microscope. However, there can be considerable variation from one sample to another. For the best results producers need to obtain twenty “grab samples” from a group of cows to accurately estimate the parasite burden.

A grab sample can be obtained riding through the pasture and observing the deposition of fresh samples. Simply invert a “zipper” style plastic bag over the sample and collect a small amount. Our current recommendation is to sample replacement heifers/yearlings and the mature cow herd separately. Younger animals have not developed the same level of immunity to parasites and can be more severely affected. It may provide a greater return to treat these two groups of animals differently.

The days of Warbex are over and parasite control in cattle is more complicated than splashing some blue tinted liquid over the cow as she runs past. Some cows, even in a relatively small geographical area, can have large parasite problems while neighboring herds are affected very little.

Parasites reduce growth, reproduction and hamper the immune system. Strategic control of parasites should return a net gain when administered timely and relative to a given parasite problem. Strategic control of parasites includes measuring current parasite infestations and working with your veterinarian to formulate effective control.


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