A limited number of dewormers — and active ingredients — are available on the market, which is why it’s important for veterinarians and cattle producers to know how each product works and how these products can best be utilized.
“Dewormers interfere with the parasite’s bodily function at the cellular level, and by disrupting that cellular function, they cause paralysis and death,” said Mike Nichols, DVM, Boehringer Ingelheim. “Producers are often encouraged to rotate parasite-control products in order to improve efficacy and enhance herd performance.”
The challenge is that you may think you’re using different dewormers, but in reality, you may not be. Macrocyclic lactones and benzimidazoles are the two general categories, or classes, of deworming products on the market, each having different chemical structures.
Benzimidazoles are white wormers that are typically administered orally. These short-acting products are generally very effective against adult worms and other intestinal parasites, but have little residual killing power.
Macrocyclic lactones have a longer duration of activity against a much broader range of parasite stages than benzimidazoles. These dewormers are available in both pour-on and injectable formulations.
“It’s important to remember that there are multiple active ingredients within each class, all of which use the same mode of action to eliminate parasites,” emphasized Dr. Nichols. “By administering a parasiticide from the opposite class, producers can take advantage of an alternative mode of action to improve deworming efficacy.”
Monitoring effectiveness of treatment can help you determine if and when using a different class of products is necessary. By performing a fecal egg count reduction test, producers can assess the effectiveness of products being used. Your herd veterinarian can advise you on the proper method and assist you with conducting the test for the most accurate results.
Barrett Franz of Bay City, Texas, is a commercial cow-calf producer with several operations along the Gulf Coast. When asked about his single best piece of advice for other cattle producers looking to improve their parasite-control programs, he explained the importance of taking fecal samples.
“If you’re not fecal-sampling your cattle prior to deworming, you’re just guessing your herd is infested with parasites, when that may not be the case,” said Franz. “We’ve gone out and taken fecal samples before, only to find out there weren’t any parasites.”
When conducting a fecal egg count or a fecal egg count reduction test, it’s also important to determine the predominant worm species present in the herd.
Concomitant therapy, a multi-pronged approach, allows veterinarians and their clients to kill a greater percentage of the parasites present in their cattle herd.
“By incorporating both macrocyclic lactones and benzimidazoles into a parasite-control program, thus utilizing two different modes of action, we can kill a larger spectrum of parasites within the herd, and more effectively reduce the risk of them developing resistance on any given pasture,” said Dr. Nichols.
When his previous supply of dewormer ran out, Franz worked with his local veterinarian to identify an alternative deworming program, which included implementing concomitant therapy.
“Utilizing an injectable dewormer with a white wormer on our calves really paid off,” said Franz. “This practice allowed us to get our fecal egg counts literally down to zero.”
Every producer’s situation is unique; no two herds are the same, and neither are their parasite burdens. With a well-planned, strategic deworming program, cattle can be better positioned to achieve increased milk production, improved feed and reproductive efficiencies, and develop stronger immune systems to fight off other diseases.