Long-Acting Moxidectin for the Control of Gastrointestinal Nematodes in Preweaned Beef Calves in Tropical Areas

Gastrointestinal nematodes (GINs) in beef calves in the preweaning period can be an underestimated problem, and an adequate control program can result in increased productivity. In the current scenario of anthelmintic resistance, clinical studies with highly effective molecules with a prolonged period of action can contribute to the development of technologies applied in the field. The objective of this study was to evaluate the effects of a 10% moxidectin formulation (10%MOX), administered to calves aged 4–5 months, in the control of gastrointestinal nematodes and weight gain until the time of weaning. The study was divided into 2 stages. The first stage was carried out on a farm, with a randomized block design based on fecal egg counts (FEC), live weight, number of calvings of the mother, breed of the calves, and pickets. In the second stage, the study was repeated on 10 other farms, following a completely randomized design, to confirm the results obtained in the first stage. In all experiments there was a treated group and a placebo group. In the first stage, the effectiveness of 10%MOX in the FECRT performed on the 38 th day post-treatment was 98.49%, and the treated animals still had lower FEC averages and a 9.4 kg increase in weight at weaning compared to those from the placebo group. In the second stage, the average increase in weight gain was 6.1 kg, confirming the results of the first stage. The study demonstrated effective control of GINs and improvement in the productive performance of calves treated in the preweaning phase, using 10% moxidectin.