Moxidectin: a viable alternative for the control of ivermectin-resistant gastrointestinal nematodes in beef cattle
2022
Borges, Dyego Gonçalves Lino | Conde, Mário Henrique | Cristina, Cibele | Cunha, Tavares | de FREITAS, Mariana Green | Moro, Elio | de Almeida, Fernando
The increasing prevalence of anthelmintic resistance in cattle especially for avermectins,is a challenge for controlling parasites in some herds. Thus, field studies demonstratingthe increase in productivity by the use of anthelmintic formulations, even when asuboptimal treatment (efficacy below 95%), can contribute to the development ofgastrointestinal nematodes control programs in beef cattle. The objective of the presentstudy was to evaluate the anthelmintic efficacy and productive performance in pastureraised beef calves, treated with macrocyclic lactones. A Split plot in time randomizedblock design was used to assess weight gain and reduction in fecal egg count (FECs)of treatments: 1% moxidectin (1% MOX), ivermectin (IVM) and abamectin (ABM)(2.25% IVM+1.25% ABM), 4% IVM, 3.15% IVM and placebo. For the evaluation ofFECs and weight gain of the animals, individual samples were collected seven daysbefore treatment and, +14, +30, +56, +91 and +118 days post-treatment (DPT). Theefficacies in the 14th DPT were: 72.3% (1% MOX) , 22.1% (4% IVM) , 22% (2.25%IVM + 1.25% ABM) and 0% (3.15% ivermectin) . 1% MOX was the only treatmentthat resulted in a significant increase in weight gain of the animals compared to theplacebo group after 118 days of treatment, with a difference of 7.6 kg. Therefore, MOXremains a viable alternative for the control of helminths resistant to avermectins andstill capable of resulting in significant productive gains, even with an efficacy below95%.
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