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Controlling parasites essential for healthy calves


A common goal among all cow-calf producers is to wean a healthy calf crop each year. With today's strong markets, producers should have great incentive to ensure their calves are raised under optimal conditions to achieve cost-effective gains.

A common goal among all cow-calf producers is to wean a healthy calf crop each year. With today's strong markets, producers should have great incentive to ensure their calves are raised under optimal conditions to achieve cost-effective gains.

An important step in that process is controlling internal parasites. Left unchecked, stomach and intestinal worms can cause production loss, reduce response to immunizations, create health issues throughout the herd, and thus, result in economic loss for the producer. Following a strategic deworming plan can help minimize the effects of parasites on cattle operations. Rather than waiting until cattle show signs of parasitism, producers should follow a deworming program that reduces infection by interrupting the life cycle of the parasite before symptoms occur.

Adult parasites produce eggs that are shed in manure, and larvae hatch from the egg. The larvae develop, become infective and are capable of migrating from the manure onto moist grass. When cows graze on the infected grass, they ingest the larvae, which then develop into adult parasites capable of producing eggs, and the process starts over again. Larvae can survive up to a year on pasture. Research conducted in the past few years at several locations in Ohio has reconfirmed overwintered larvae can create heavy worm burdens in ewes and lambs, and this can result in severe disease as early as mid-June. In addition, adult animals can provide a new generation of infective larvae in the spring with the eggs they deposit on pastures in their manure.

Parasites can result in production losses, ranging from depressed feed intake and conversion, reduced weight gain, lower milk production and lower reproductive performance. They also can have negative effects on immunity and cause visible, disease-like symptoms, including anemia, edema, diarrhea and more.

To achieve the best return on investment in a deworming program, it is important to deworm cattle when it is most effective. Parasite burden peaks during the spring when grass is wet from rain or dew and is lowest during hot summer months when grass is typically drier. Larry Hollis, KSU Extension veterinarian recommends the clean cow-clean pasture concept. That's his answer to the question of when you should worm your cows.

"When you go to clean pasture, put clean cows out there," Hollis said.

That way, he said, you reduce the level of egg and larvae contamination in the pasture, which is the major source of the worm load that cows, and eventually their calves, will carry.

Hollis stresses the word "reduce."

"No dewormer is 100-percent effective, so over time, there will gradually be a buildup of eggs that hatch into infective larvae. But you'll minimize that to the smallest degree you possibly can if you'll deworm them when you go to clean pasture," he said.

That means deworm your cows when you turn out in the spring and then again in the fall, ideally after the first hard freeze if they're using winter pasture.

Young calves are at highest risk for parasite problems, making appropriate deworming even more crucial. Studies have shown effective deworming programs can provide 20 or more extra pounds of gain per grazing season.

A number of good dewormers are available now, but producers need to make sure the product they use is a good match for the target parasite. Read the label and talk to your veterinarian to insure the appropriate wormer is used for the parasites they're packing around.

How the dewormer is administered also is important. Pour-on and oral feed forms are convenient, but the amount that each animal gets can be highly variable.

"If you're really after worms, use the injectable form," Hollis advises. "A lot of people like to use pour-on for convenience, but those will never do as good a job of deworming as the injectable forms of the same product.

"Ivomec injectable will do a better job, hands-down every time, than Ivomec pour-on, and the same thing with Dectomax."

The other thing producers need to watch is dosage, Hollis said.

Producers tend to deworm their herds based on an average weight and that can mess them up a bit.

"The average weight of beef cows across the U.S. is now about 1,400 pounds. Most people don't realize that," he said.

If a producer has some 1,600-pound cows and some 1,100-pound cows, but is treating for a 1,200-pound average, it's going to result in uneven dosing.

There's growing evidence that internal parasites are developing resistance to some dewormers, and experts believe under-dosing might be a primary cause. Few cow-calf operations are set up to weigh each individual animal, so what's a producer to do?

Some experts now recommend the dosage be based on the heaviest animals in the herd rather than an average.

"You need to make sure your bigger animals are getting enough to treat them effectively," Hollis said.

Your veterinarian will be a great partner for developing a strategic deworming plan for your herd.

Stacy Campbell is agriculture Extension agent in Ellis County.