Parasite control can require pasture-specific practices

April 06, 2016

For any cattle operation, controlling parasites is critical to herd health. Cattle with strong immune systems have a better shot at reaching their genetic potential and as described in a recent article, more pounds on the ground will equal more money in the bank if all goes according to plan. What isn’t so simple, however, is coming up with a parasite control program that is cost effective for an individual herd.

According Tom Craig, DVM, parasite control is not a one-size-fits-all formula.

“The first thing you have to analyze is your location,” Craig said in the article. The reason this has to be your first priority is because a parasite will react differently at the same time of the year in Texas than it will in North Dakota, for example. Narrow it down even further, and the parasite will react differently in as little a distance as from the middle of the pasture to the fence line, depending on water and vegetation.

The next factors you have to address are: What age of animals do you have, what is your stocking rate and density, and what is the quality of your pastures? In the article, five veterinarians from around the country discussed what was most important for beef producers to keep in mind when planning a parasite-control program. As a general consensus, beef producers must develop a veterinarian-client-patient relationship first, to make parasite control work cohesively with their other herd-health practices.

“I think it is a unique opportunity for veterinarians to not only work with their clients on parasite control but all aspects of their operation,” Glenn Rogers, a veterinarian consultant and Texas rancher said. “Parasite control must fit in with all other animal-health inputs. There should be a standard protocol for vaccinations and deworming for every animal that comes on the farm or ranch,” he added.

Each pasture can offer significant differences in parasitic environments. “Parasites are local, and they play the game in a local way,” Craig explained in the article. Because of this, producers should work with their veterinarians to address the best parasite-control protocols for their environment.

While parasites all play the game differently, there are four common players that make appearances in multiple parts of the country.

  • Ostertagia ostertagi – Known as the brown stomach worm, it’s one of the most important gastrointestinal parasites and lives in the abomasum or true stomach of cattle. “It lives in the glands that produce the chemicals or enzymes necessary to render food into nutrition,” Craig said. When the worm is still immature, it will go into the gland and grow into an adult within a matter of a couple of weeks. Once it emerges, the gland will not function properly for up to two months, leaving the host with potential weight loss, lower feed efficiency and even reproduction inefficiency in cows.
  • Haemonchus placei – Stretching out to 18 mm long for a male and 30 mm long for a female, these stomach worms aren’t anything to mess with. According to Craig, this worm will make a home in the stomach and suck a lot of blood. “If these are in your cow–calf herd, the cows become resistant, but calves, especially dairy calves and stockers on permanent summer pasture, will be at a higher risk for clinical diseases,” he said.
  • Cooperia – Several species of this gastrointestinal parasite can be found hanging out in the small intestine of cattle. They will interfere with the absorption of nutrients which can lead to diarrhea. “The big problem with Cooperia is in younger cattle, since the animal can become resistant when they are around two years of age,” Craig explained.
  • Oesophagostomum radiatum – This worm is almost as long as its name — with an average length of 12 mm to 15 mm long. Cattle get these two ways: First is by eating the larvae on vegetation after a rain or heavy dew, Craig said. “But this parasite can also penetrate the skin under the right circumstances and migrate to the upper large intestine where they emerge as adult worms.” In the intestine, the worms will find a mate and lay eggs. However, the real damage is done during migration to the intestines. The animal’s immune system will form a puss pocket around the worm to kill it. Once that is done, the pocket will calcify and can cause damage to the intestinal tract.

Treatment options were also discussed in the article, including the best time to deworm your cattle.

“When you are trying to design a health-management program, you have to not just look at parasite cycles, because we’re typically not going to deworm at exactly the right time,” Rodgers said. “It’s got to be given in conjunction with other practices that are done on that particular operation.”

Depending on production environment and climate, cows and calves should be treated in the spring before they are turned out to grass, so parasite eggs wouldn’t be shed in green pastures. Also, animals should be treated once again in the fall to kick out any parasites picked up from summer pasture, the article explains. In addition, producers should go with products that are proven to work since going only off price may not result in a product that is as effective, leading to the parasites building a resistance to products.

Producers also have to decide if they want to use injectable, pour-on or oral products. According to Rogers, only 15% to 20% of pour-ons will be absorbed, compared to 85% to 90% of injectables. “You have the lickers and the lickees. The lickers get a bigger dose… as soon as they get poured, calves can lick it off, or the cow can lick it off, and they’re underdosed,” he said.

A full spectrum of control is key. “Parasite distribution in cattle is a lot like money distribution in people,” Craig says. “A few will have a lot, but most will have very little.”

And while Craig sees use for both pour-ons and injectables in herds, he recommends producers don’t use the same treatment method on cows as they do for their calves, reserving injectables for cows.

“I don’t want to use most of the injectables for calves—unless it’s under the right circumstances after they have been weaned—but if a calf is suckling, give it something oral,” he says. “We want to make sure a few of the worms from the cows get through so we have enough to stimulate a protective immune response to build resistance. Also the pour-on and injectables may be ineffective against Cooperia, which can be important in calves.”

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