Effective parasite control in stocker operations includes everything from pasture management to herd health and nutrition to the seasons and specific environments. Here, though, we’ll focus on using deworming products.

For economic perspective, the groundbreaking Economic Analysis of Pharmaceutical Technologies in Modern Beef Production estimated stocker breakeven prices would increase 2.7% without the use of dewormers, at a cost of $20.77 per head. Keep in mind that was almost 15 years ago, when 6-weight steers averaged in the neighborhood of $120 per cwt at Oklahoma City.

Even when dewormers are utilized, improper use dilutes the bottom line, and in some cases contributes to parasite resistance.

“You wouldn’t take a five-dollar bill and throw it on the ground. Why would you do that with your dewormer? Take just a little extra time to apply the product correctly,” says Ty Brunswig, DVM, of the Animal Medical Center at Great Bend, Kan.

Brunswig was part of a panel addressing parasite control at this fall’s Kansas State University (KSU) Beef Stocker Field Day. He was referring to the occasions when folks seem to approach cattle processing as a timed event.

“Wherever it lands, that’s the animal’s fate and then we move on,” Brunswig said of those who spray a topical dewormer in one spot, rather than applying from withers to tail head.

Similarly, although everyone knows deworming products need more care than, say, a rock, A.J. Tarpoff, DVM, KSU Extension veterinarian, continues to see jugs tied to the side of too many chutes, the hose filled with product.

“These are temperature-controlled products that we have to take care of,” says Tarpoff. “Sunlight will break them down. If they get too hot, they start to break down.”

That’s before considering dosage.

“We get a lot of calves at the stocker unit (KSU) that are supposed to be like-sized, and we have a weight difference top to bottom of 300 pounds,” Tarpoff says. If they dosed on the average weight, he explains they could be under-dosing a percentage of the group by as much as 200 pounds.

“When we under-dose, especially with parasiticides, that’s where we can really run into resistance issues (see below), even if we’re doing everything else the right way,”  Tarpoff says. That’s also why producers may think the deworming product is less effective than expected.

In a perfect world, you’d know exactly how stocker cattle were handled prior to arrival and which parasites each calf harbors, then you’d treat each accordingly.

“There are a lot of different things we take into account,” Brunswig says. “It’s what kind of cattle we’re looking at, where they came from and what time of year it is. Were they backgrounded previously; did they come from a ranch down the road that we know uses a pretty good processing protocol? Most of the time, we don’t know those things.”

Brunswig estimates 99% of the stocker cattle he services for clients are high-risk cattle out of the Southeast.

“Every program I deal with, if it’s high-risk cattle, they’re getting dual dewormed with a white wormer orally and a topical macrocyclic lactone,” Brunswig says. He adds that the nature of intensive stocker operations makes it difficult to utilize fecal egg testing to help make decisions.

“These high-risk cattle, the vast majority, are coming in with a high load of internal parasites,” says Tarpoff.  “Because of that, I know it’s going to hinder immune function because the immune system will try to fight these parasites instead of responding to the vaccines I’m giving. I know it’s robbing some of those calves of protein digestion, energy, everything.”

Preserving dewormer use

Using parasite control products judiciously and according to label also delays resistance and preserves their use.

There is no national statistic for anthelmintic resistance in beef cattle in the United States. However, various analyses, such as fecal worm egg count reduction trials, suggest growing parasite resistance to common anthelmintic classes. Globally, resistance is recognized as a key threat to grazing livestock.

“Anthelmintic resistance has been a recognized problem in small ruminants for decades. Now there is increasing concern about resistance of cattle parasites to dewormers and the ability of cattlemen to continue to have cost-effective parasite control,” explains Christine Navarre, DVM, Extension veterinarian at Louisiana State University (see “Finding the deworming sweet spot").

In fact, resistance is enough of a concern that late last year the FDA requested animal drug companies to revise, voluntarily, the labels of drugs intended to treat certain internal parasites in livestock and horses by adding information about antiparasitic resistance.

“Any use of a dewormer can result in the development of antiparasitic resistance,” according to the FDA statement. “Proper dosing is critical to the safe and effective use of a dewormer. End users should work with their veterinarian to monitor herds and flocks to determine the extent of antiparasitic resistance on a particular farm. Dewormers should be used as only one part of an overall internal parasite control program.”

“It doesn’t tell us anything new, but I think it does bring to light that we should reassess how we use these products to ensure that we’re using them appropriately, to make sure we’ll be able to use them long term,” Tarpoff says. “We can put the blinders on, but we’re not getting new parasite chemicals coming down the pipeline; I’m doubtful there will be any coming soon. I want to make sure we can use them into the future.”