Add to favorites

#Research & Development

Combination Plan

Dewormer Found to Have Activity on Horn Flies

LongRange was introduced to beef producers in December 2012, as the first extended-release injectable cattle dewormer providing up to 150 days of parasite protection. But the Merial product looks to be more than a dewormer, judging by a recent study.

A team of independent researchers, working in the Kansas Flint Hills, found the dewormer also works against horn flies. Dale Blasi, beef cattle specialist at Kansas State University, said the project looked at 301 head of stockers (heifer short yearlings) on Flint Hills pasture. Average weight was 587 pounds. Gains over a 90-day period ranged from 110.31 pounds under no treatment; to 144.17 pounds for a treatment that included LongRange plus the implant Revalor-G.

Blasi noted steers would show even greater gains, explaining they used heifers in the project because at the time that was the best economic choice for their cattle producers. He added all product was donated by three manufacturers -- Bayer, Merck Animal Health and Merial--but said the work was independent and driven by the team.

"We previously evaluated LongRange for worm control, as that was how it was initially marketed," said Blasi. "Now we are seeing it is beneficial as a fly control, and some of the gains we saw on those stockers were due to that. Those calves went onto pastures clean. They had been dewormed with Safe-Guard [fenbendazole] in early March, and remained in pens until being placed on grass. So we believe we can attribute gains in the LongRange group to horn fly control."


Nine treatments were studied by the team, including one where stockers received no fly control or implant. The goal was to keep horn flies below economic threshold levels (200 flies per animal). Horn flies are costly for the beef industry, exceeding $1 billion each year in losses and treatment costs.

The top three yielding treatments included: (1)LongRange + Revalor-G; (2)Corathon fly tag + Revalor-G; and (3)LongRange + Ralgro.

When LongRange was combined with the implant Revalor-G, the pair yielded average daily gains (ADG) of 1.60 pounds on stocker calves, for a total average 90-day gain of 144.17 pounds. LongRange was administered at 1 ml per 110 pounds. Estimated cost for the combined treatment is $8 to $9 per head.

A Corathon fly tag plus Revalor-G yielded an ADG of 1.50 pounds per head, for a total 90-day gain of 135.32 pounds. Estimated cost for this combined treatment is $3 to $4 per head. Lastly, LongRange plus the implant Ralgro yielded an ADG of 1.50 pounds per head, for a total 90-day gain of 134.59 pounds. Estimated cost for this combined treatement is $8 to $9 per head.

How much of the gain seen was due to the implant, and how much to the second product? Justin Talley, Extension livestock entomologist at Oklahoma State University, described what happened as an additive effect, and noted the implant combined with an ear tag was statistically no different in ADG than the implant combined with LongRange.

Of the two groups that only received implants (no fly treatments), Ralgrow returned an ADG of 1.31 pounds per head (117.62 over 90 days). The Ralgrow plus LongRange treatment showed an additional 16.97 pounds of gain. In the case of Revalor-G alone, ADG was 1.42 pounds per head (127.68 over 90 days). The Revalor-G plus LongRange treatment showed an additional 16.49 pounds of gain.

Talley noted LongRange's activity on horn flies had been reported anecdotally for the last couple of years. In the study, he added, they were surprised at how well the control worked.

"We know that anything with Ivermec in it will have activity on horn flies, but we saw good control all the way to 10 weeks post-treatment," said Talley. He pointed out the use of LongRange strictly for horn fly control is still off-label, and he stressed the continued importance of rotating fly controls based on mode of action.

"Consider why you are using LongRange. First would be internal parasites. So if you use it as your dewormer, I'd rotate fly control. Don't just use Ivermec-type products. Give LongRange in the spring for internal parasites, then come back in late summer with a pour-on for fly control that won't stay in the environment as long and has a different mode of action."


  • United States
  • Victoria G. Myers