Sponsored By

Timing Is All-Important For An Effective Parasite Control ProgramTiming Is All-Important For An Effective Parasite Control Program

It pays to know the parasites you’re dealing with in order to pick the right dewormer to control them.

Larry Stalcup

March 27, 2013

10 Min Read
Timing Is All-Important For An Effective Parasite Control Program

“Cattle just don’t gain.”

Missy Bonds’ analysis of cattle infested with parasites describes the damage the tiny creatures can have on all cattle. Thus, she’s a firm believer in dewormers and their value in a cow-calf or stocker program.

“The $5-$10/head cost of deworming a cow and calf at branding can mean an extra 50 lbs. for the calf, and better body condition and breed-back on the cow,” Bonds says. Her family’s Bonds Ranch, headquartered in Saginaw, TX, has a detailed parasite control program for its wide range of locations.

The sprawling operation includes pastures in 26 Texas counties, as well as Oklahoma, Kansas, New Mexico, Colorado, Nebraska, Iowa, South Dakota and Montana. They also have operations in Mexico and Canada. Thus, climate can vary from semi-arid to more humid, and hot to cold; and each area may require a parasite program different from another.

Missy, whose father Pete Bonds was BEEF magazine’s 2011 National Stocker Award winner, helps map a parasite plan by region. “Some areas see few parasite problems; others require treatment 3-4 times/year,” she says.

Brown stomach worm

The brown stomach worm (Ostertagia) is a parasite that gets Bonds’ attention more than most. “It’s the most economically significant, and quite prevalent in Texas and much of the country,” says Jerry Woodruff, senior veterinarian for Boehringer Ingelheim Vetmedica, Inc. (BIVI).

Rich Linhart, Zoetis managing veterinarian of beef technical services, says it’s very important to identify parasites that effect your herd, but it’s also important to consider what stages of a parasite’s lifecycle a parasiticide is effective against. “How, and more importantly when, parasiticides are administered is critical in achieving the maximum benefit from a strategic deworming plan,” he says.

A Closer Look: Exactly When You Deworm Your Cows Matters

As an example, Linhart says it’s not wise to use a parasiticide that’s ineffective against a certain stage larvae at a time of year when those larvae are present or predominant. “A better choice is to select a product that’s effective in controlling many species and stages of parasites, and use that product at a time of year that returns the most benefit in terms of pounds of beef gained.

Ostertagia and Cooperia species both impact cattlemen’s bottom line. Failure to control the inhibited and uninhibited L4 larvae of Ostertagia can contribute to re-infection and failure to achieve the full economic benefit of a parasite control program. Most products will eliminate the adult forms of Ostertagia; the same cannot be said for control of the larval stages of the parasite,” Linhart adds.

Mike Mustian, a BIVI territory manager who works with Bonds, says the worse the brown stomach worm infestation is, the more that animal’s appetite is decreased. “It’s important to get cattle treated early before heavy forage growth,” he says.

Although some regions have faced drought, areas where even small amounts of rainfall or snow have occurred can see a quick rebound of grasses. “Even heavy dew can promote worm transmission,” Mustian says. “The worm only needs a droplet of water to get on that blade of grass. When cattle start grazing, parasites can start harming them internally.”

Dewormer persistency

Bonds says cows are normally treated with a pour-on at gathering time or anytime they’re in working pens. Also, calves are injected with a dewormer at branding and given a pour-on and a white paste (drench dewormer) at weaning.

“One deworming will sometimes be sufficient in an area where the climate is drier,” she says. “But to be safe, we also treat cows with a white-paste dewormer when we palpate, as she’s already in the chute. The white paste provides an immediate kill.”

Woodruff says persistent control provided by a dewormer should be considered when selecting a parasite control product. “Persistency describes how a dewormer continues to fight parasite infestations after application,” he says. “Increased persistency can result in fewer parasite eggs shed, reduced pasture parasite levels, and increased opportunities for weight gain.”


Bonds uses primarily Cydectin® pour-on or injectible, as well as Synanthic® white paste, both from BIVI. She sometimes also uses a different white paste, Safeguard® from Merck. A producer’s dewormer arsenal may also include Dectomax® from Zoetis, Noromectin® from Norbrook, and Merial’s Eprinex®, Ivomec® and a new product called LongRange®.

Harold Newcomb, Merck Animal Health technical veterinarian in northwest Mississippi, says the use of two or more separate classes of dewormers in a concurrent treatment program can help prevent or control parasite resistance.

“There are three classes of anthelmintics (wormers) approved for use in the U.S.,” he says. “They include marocyclic lactones, which consist of injectible and pour-on products such as Ivomec, Eprinex, Moxidectin and generic ivemectin products; the benzimidazoles, which are the white anthelmintics such as Safeguard, Valbazen® and Synanthic; and imadathiozoles, which are Levamasole and Rumental.”

Newcomb says National Animal Health Monitoring System (NAHMS) data indicate that parasite resistance is increasing in the U.S. He adds that concurrent class use, along with pasture and animal management, has shown to decrease anthelmintic resistance in Australia and New Zealand. 

“Concurrent class use seems to work,” he says. “That’s because the number of parasites with genes with resistance to one class of anthelmintic is greater than the number of parasites with genes with resistance to two classes, and the number of parasites with genes with resistance to all three classes of anthelmintics. Using two or more classes concurrently reduces the number of resistant parasites.”

Newcomb says parasite control is the cornerstone of any herd health program, as parasites affect every segment of the beef industry. “The economic impact of parasites was estimated to be up to $195 over the lifetime of a calf in a recent study by Iowa State University,” he says.

Fecal samples

“One of the key components to any deworming program has to be a fecal egg count reduction test (FECRT),” Newcomb says. “The FECRT is the only way at present for the producer to monitor the efficacy of his deworming program. Since no two operations are alike, every producer should work with their veterinarian or cattle parasitologist to develop a deworming program that meets the specific needs and goals of their operation.”

The FECRT is a herd-level test, points out Roberto Cortinas, DVM and assistant professor in the University of Nebraska Lincoln (UNL) School of Veterinary Medicine and Biomedical Sciences. “At least 25 animals should be randomly sampled, preferably from the same age class, before and after deworming. You don’t have to sample the same individuals – you’re sampling the herd for overall reduction in egg production.”

A Closer Look: Controlling Parasites Doubly Important In Time Of Drought

Bonds says their stockers are dewormed upon arrival, either with an injectible or a pour-on. If needed, a second treatment is given 30-60 days later.

“We determine whether a second or third treatment is needed by collecting fecal samples,” she says. “We also read reports of different regions and pastures with our drug rep. We can see which pastures will require cattle to be dewormed and which one doesn’t.”

Woodruff says fecal egg counts (FEC) are a widely used method of evaluating internal parasite infestation. “FEC is performed by mixing a known volume of feces with either a saturated salt or sugar solution, allowing parasite eggs to float to the surface where they can be captured on a microscope slide,” he says.

Parasite eggs can then be evaluated and counted. FEC results are normally reported as eggs per 1 gram of feces, Woodruff says, adding that “misunderstandings about the level of parasite infestation occur with FEC results reported as eggs per 3 grams, or eggs per 5 grams, of feces.”

FEC is relatively inexpensive and easy to accomplish. But another process called “coproculture” identifies specific internal parasites present. “Coproculture is performed by incubating the fecal sample for 2-3 weeks and allowing eggs to hatch into larvae,” Woodruff says. “The larvae can then be classified as to genus and species.

“Knowledge of which species of parasites are present is important, since some internal parasites are considered more pathogenic than others, and some are more proficient egg producers. Coproculture results aid in tailoring a dewormer program specific to the family of parasites present in a group of animals.”

A follow-up FEC determines the effectiveness of initial dewormer applications, he says. It normally involves testing of two fecal samples from the same animal, collected 10-14 days apart. A calculation can then be made as to the percent of reduction in internal parasite eggs.

Cortinas adds that UNL’s Veterinary Diagnostic Laboratory is in the process of instituting a polymerase chain reaction (PCR) test that will provide quicker results than coproculture. “It can be done right when we do the fecal exam without having to wait for the eggs to hatch, which can take 1-2 weeks,” he says. Colorado State University also offers the PCR test.

Woodruff says timing of the follow-up sample is important to accurately assess effectiveness of a parasite control product. “Adult parasites not removed by treatment may suspend shedding eggs for several days after exposure to the treatment drug, thus artificially underestimating remaining parasite levels,” he says.

“If the second sample is collected much past three weeks post-treatment, it could possess eggs from newly acquired infestations. There could be egg-shedding variations due to diet change effects on the adult worm; or in the case of inhibited Ostertagi, a new crop of larvae may have developed into mature, egg-laying adults.”

Bonds says her operation virtually always takes an FEC when a pour-on is used. “Also, we like using pour-ons when flies are an exceptional problem,” she adds. “We see some extra fly control.”

Mustian says producers and stocker operators should also consult their vet and animal health reps to look for Cooperia worms. “In wet, low-lying areas, you also need to look at liver flukes,” he adds.

Mustian notes that in some parasite control programs, three applications may be needed. “If you’re going by the book, there should be two applications – one in late spring or early summer, and one in the fall near November,” he says. “If you spend the money on a good deworming program, it may pay you back 3-4 times over.

“It’s not only important for gain, but for animal health. If cattle have a heavy worm load, they don’t respond as well to a vaccine,” he says.

Spring parasite control is vital

With late winter snow and spring rains, pastures rebound from their winter nap to yield fresh forage for herds. But those grass blades can be host to parasites that can ruin cow and calf performance.

Joe Dedrickson, veterinarian and director of Merial Field Veterinary Services, says, “Producers can’t afford to take chances with a health practice such as parasite control.”

Research by Iowa State University (ISU) and others illustrate the value of a good dewormer program. ISU studies show that parasite control tops the list of the most economically rewarding cow-calf pharmaceutical practices. And, not controlling parasites can negatively impact a cattle producer’s breakeven by up about $200/head.


Enjoy what you are reading? Subscribe to Cow-Calf Weekly for the latest industry news every Friday.


“Merial recognizes that, in a tight economy, it’s difficult to justify input costs if you aren’t sure you are getting enough return. But nothing pays off like parasite control in the spring,” Dedrickson said, in comments during the recent launch of Merial’s new LongRange® (eprinomectin), an extended-release injectible cattle dewormer.

It’s important to consider timing when developing a deworming protocol, he adds. “Controlling parasites at spring turnout is an important cost-effective way to boost calf weaning weights and gain reproductive efficiencies in cowherds,” Dedrickson says.

Since every producer’s situation is unique, he recommends consulting with a veterinarian when developing a deworming strategy. “The time of year when grazing season begins, age and category of the animals, type of operation and grazing history of the pasture are all considerations to discuss,” he says.


You might also like:

10 Best Steak Houses, PLUS 3 Awesome Beef Cookbooks

Controlling Parasites Doubly Important In Time Of Drought

Research Finds No Bull Fertility Difference With Pyrethroid Use

Outsmarting Flies On the Ranch

Subscribe to Our Newsletters
BEEF Magazine is the source for beef production, management and market news.

You May Also Like