ROTATING CHEMICALS LOWERS RISK OF PARASITE RESISTANCE

by: Clifford Mitchell

Parasite control or maintenance is just one of the many tools managers have to improve performance in the beef herd. Internal and external parasites impact production goals. High priced inputs such as feed and fertilizer change the demeanor in which some managers approach this task.

Environment or region of the country makes treatment for parasites a little diverse because cattle are affected by different vermin at distinct times of the year depending on several factors. Location, weather patterns and time of year will impact the type of internal and external parasites that can be harmful to the cow herd.

“There are distinct seasons for worm transmissions, depending on climate and weather patterns. Worms are unique because they have to cycle through the environment. They aren't the most damaging parasite though, lice and horn flies are external parasites than can take their toll,” says Dr. Craig Reinemeyer, President East Tennessee Clinical Research.

“You can't just name a date for de-worming and other parasite control. Year-in and year-out there are changes that leave room for error. Watch the conditions. Check when you quit getting frost and start getting some moisture. Days and weeks are a long time in the parasite life cycle and parasite loads can increase rapidly if not controlled at the proper time,” says Dr. Jane Parish, Extension Beef Specialist, Mississippi State University.

Pasture management is a big part of successful beef production and may be the first step in limiting internal parasite loads. Stocking rates, moisture and the ability to rotate pastures will also help define how operators can limit larvae ingestion.

“Parasite larvae tend to stay within two or three inches of the ground, so try not to graze pastures too close. The time of year, rainfall and how heavily stocked an operation is, could cause overgrazing,” Parish says. “Managing pastures where more residues are left will help limit larvae ingestion. Moving cattle to fresh pasture every 45 to 60 days will also help control parasite loads.”

“Worms don't really care about your management schedule and how you do things. Worms pay more attention to the environment and the time of the year. They are more prevalent at certain times depending on where you live,” Reinemeyer says. “Worm eggs pass in the manure and through pasture management systems.”

The effectiveness of control depends not only on the product, but also on the timing of management. Limited labor resources play a role in management decisions, often times, causing problems because timing treatments wrong can lead to other problems.

“Producers get a lot more bang for their buck when they follow seasonal treatment recommendations. A lot of producers go for convenience and when they have cattle up, there's a good chance they are going to de-worm them,” Reinemeyer says. “If you don't do it at the right time efficacies are going to be compromised. When you de-worm at the right time with the right product, parasite loads will decrease.”

“When you can knock down worm loads, you can pay for that de-wormer and your labor costs easily with increases in performance. It doesn't always pay to de-worm every time you put cattle through the chute,” Parish says. “If you suspect heavy parasite loads, because of poor gains, hair coat or body condition score, it might be time for more treatment or to consult your veterinarian.”

Changing chemicals is a must, whether cattlemen are combating internal or external parasites. Different factors, such as price, influence purchase decisions. Accurate records and asking for help should help commercial operators properly control parasites.

“Whether it's fly control or de-worming, producers have to follow the rules and change chemicals to avoid building resistance. Cut those fly tags out because flies have rapid life cycles and can become resistant quickly. You have to watch those fly loads depending on the year and sometimes one fly tag will not last the whole season because some products don't have lengthy control or the fly season is exrended,” Parish says. “Rotate the active ingredient in those de-wormers. Some folks get in the bad habit of going to the same place every year and buying the same product because it's on sale or get caught using up last year's good deal this year. Be flexible and use other products when you're supposed to.”

“Anthelmentic resistance is starting to become a problem in the beef industry. This has come about because of two things: generic components that make it cheaper for cattlemen to de-worm so therefore they do it more often and using the same class of de-wormer over and over again, primarily because of convenience,” Reinemeyer says. “Producers have to keep rotating families of drugs to control internal parasites. An oral drench treatment is actually the best way to treat cattle. De-worming cattle often to increase performance has probably contributed to resistance. The product is approved to kill worms not enhance production.”

Timing is not the only thing producers need to be concerned about when they use products to control internal parasites. Label instructions are important to get the proper dosage.

“Under-dosing is a big problem in our business and is another contributing factor to resistance,” Parish says. “Know the proper dosage and administer it correctly. Some producers will need a set of scales to make sure they accurately dose those cattle with treatment.”

Different classes of cattle can be more susceptible to resistance. By defining production goals and paying close attention to the beef herd some operators may be able to design strategies that will redefine how they approach controlling internal and external parasites.

“Fecal egg counts are a great way to test resistance. Take a pre-treatment fecal sample and in 10 to 14 days take another sample from the same cattle. If you have anything less than an 80 percent reduction of fecal egg counts the worms have developed anthelmentic resistance. Fortunately, the worms that are building resistance aren't very harmful to beef cattle, but that may not be the case in the future,” Reinemeyer says. “Stocker operations usually have the most potential to develop resistance, because they have been told to give more frequent treatment and they have seen increases in gain. Some classes of cattle don't need de-worming. Mature cows are pretty resistant to worms. Calves get immunity from there mothers when they're still sucking. It's really important to control parasites as those cattle are growing. Particularly from the time they are six-months until they are two-years-old. It probably makes more sense from a profit standpoint to control horn flies on mature cows than to de-worm them.”

“Usually when we see our vet it's time to get health papers. People are going to have to start having those conversations with their vet about what products are available and how important it is to rotate these products,” Parish says. “It's not like you can see the worms with the naked eye. You have to pay close attention to hair coat, body condition and even get fecal egg counts to know if the control program is effective.”

Soil samples have become increasingly important as fertilizer costs continue to rise. Farmers take advantage of technology like GPS to make sure they can improve efficiency and a new term called precision agriculture helps only give the ground what it needs, when it needs it. Farmers reach production goals and control costs.

“You hear about farmers taking extra steps with precision agriculture. A soil sample is a good example because you put out what fertilizer you need. Maybe beef producers are going to have to take the same approach,” Parish says. “Some genetics will obviously have more resistance to certain parasites built in. Cattle get used to different parasites and can handle different parasite loads. Animals that are new to the environment may require extra attention. Fecal egg counts help document continued maintenance and could help a producer say this group doesn't need to de-wormed right now. This limits the chance resistance could build up in that herd.”

Cell phones, computers and other forms of advanced communication have made it easier for some to communicate. For the passerby, who could be an enemy of agriculture, makes beef producers an easy target. Managing internal and external parasites puts the best foot forward in the public's eye and could also have an impact on the bottom line.

“Parasite maintenance is mainly worms and liver flukes depending on your area. Biting insects can bring other problems like anaplasmosis,” Parish says. “Rotating chemicals and proper timing will help increase performance, limit affects of disease spread from biting insects and provide a positive image for our enemies. Increased external fly loads and poor body condition caused by heavy internal parasite loads don't give the casual passerby a good image.”







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