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Deworming in the Fall Pays Dividends

NEW YORK (Sept. 28, 2009) – Since 2004, Iowa State University researchers have been reporting on the impact of pharmaceutical technologies in cattle operations. Time and time again, deworming has shown a positive return on investment (ROI) for producers with the latest data showing a $201 per head return in cow/calf operations and $24 per head return in stocker operations.

Because parasites prefer warm, moist climates for optimum production, intervention procedures to help capitalize on that positive ROI vary greatly from the northern to southern parts of the United States.

“Generally in the North, these conditions occur in the spring then decline with the warmer, dry summer conditions. The conditions may reoccur in the fall then go into a prolonged inhibited state over the cold winter,” says Jon Seeger, DVM, Pfizer Animal Health veterinarian. “However, in the South, the fall is the optimum time for parasite development followed by the cooler winter grazing period and the inhibition occurs during the longer, very warm and dry summer.”

By recognizing the differences between regions, producers can evaluate their program to develop the correct protocols and take advantage of the return on investment dewormers can offer. Pfizer Animal Health veterinarians Jon Seeger, DVM, from Turtle Lake, N.D., and Glenn Rogers, DVM, MS, DABVP, from Aledo, Texas, offer the following tips and advice for producers to follow depending on their geographic area.

Selection of a Deworming Product

When selecting a dewormer, Seeger recommends focusing on the following criteria: purge or strategic intent, injectable or pour-on application, the time of year of administration and whether internal or external parasites are the target.

If purging the animal is the intent, administering a dewormer with a shorter duration that gets the job done will do, but strategic deworming requires a longer-lasting product to adequately prevent further cycling of parasites on pastures.

Rogers adds that producers should take into account the following things when selecting a deworming product: efficacy, consistency, persistence, convenience, cost benefit and support.

Rogers also recommends the following rules of thumb in relation to deworming products:

- Injectables are a better choice vs. pour-ons when treating internal parasites.

- Injectables should be used over pour-ons in young animals.

- Pour-ons are a better choice for lice, particularly biting lice, and fly control.

- Pour-ons are more convenient in most cases and reduce the number of injections.

Recommendations for Northern States

According to Seeger, fall deworming in northern states is usually conducted to clean up internal parasites that have accumulated during the grazing season, and to improve production, feed efficiency and responses to immunizations. Deworming in the fall also gives northern producers an excellent opportunity to control external parasites, like lice and grubs, and eliminate inhibited larvae from internal parasites, like Ostertagia and Cooperia.

“Inhibited larvae occur in the North when parasites recognize that things are going to get a little tough if they are passed out on to the cold, snowy ground,” explains Seeger. “They actually burrow into the animal’s stomach glands and wait out the winter, meaning cattle can still be infected with parasites in the spring.”

When selecting a specific dewormer and developing protocols for fall deworming in the North, there are a number of factors to consider. For instance, producers should pay attention to the class of cattle being dewormed.

“If you are deworming spring calves for sale, there may be an advantage in deworming relatively early in the preconditioning program to enhance later viral vaccination and to allow time for a bit of additional weight gain,” explains Seeger. “An injectable dewormer might be the best choice in this case.”

For adult cattle that are going to be wintered on site, a later application of a pour-on dewormer is a better choice. This allows for controlling grubs, lice and inhibited larvae that the cattle will be exposed to during the winter.

Challenges in the Southern States

The southern United States doesn’t have the defined pasture seasons that are found in the North, so producers are deworming in the fall due to the larval build-up on pastures during the summer. “The killing frosts don’t kill worm larvae on pasture as was once thought, so transmission can occur during the winter,” says Rogers.

Specifically, fall deworming in the southern states is for internal parasites Ostertagia, Haemonchus and Cooperia. Lice are the external parasites that should be targeted. If an area is prone to fluke infection, producers in fluke areas should treat cattle between September and November with a flukicide.

“There are no blanket recommendations when it comes to parasite control,” shares Rogers. “Each protocol should be tailored to the operation in question. Consideration should be given to control of economically important parasites through a strategic, customized plan that fits the operation’s forage, management and labor resources.”

Rogers adds that a treatment is strategic if it happens when the greatest proportion of the total parasite population is in the cattle, and not on the pasture.

“Deworming at the wrong time may produce marginal results, even when the best products are used,” says Rogers. “It is important to have a thorough understanding of the economically important gastrointestinal nematodes on a specific ranch and match strategic application as closely as possible with other cattle handling events, such as pregnancy checking or weaning.”

Seeger and Rogers both recommend that producers contact their local veterinarian, animal health supplier or Pfizer Animal Health representative to develop a complete parasite control program.

Pfizer Inc. (NYSE: PFE), the world’s largest research-based pharmaceutical company, is a world leader in discovering and developing innovative animal vaccines and prescription medicines. Pfizer Animal Health is dedicated to improving the safety, quality and productivity of the world’s food supply by enhancing the health of livestock and poultry; and in helping companion animals live longer and healthier lives. For additional information on Pfizer Animal Health’s portfolio of animal products, visit