Avaliação andrológica de touros nelore (Bos indicus) tratados com ivermectina 4%

Abstract

Based on farmworkers personal communication about fertility reduction of bulls treated with ivermectin 4%, as well as their setback in treating this animal category with this product, we hypothesized that this drug may affect breeding soundness evaluation (BSE) results of bulls, although, this influence may be temporary. Thus, this study aimed to evaluate these effects in Nellore bulls. Twenty-two bulls were randomly assigned to the experimental group. In order to include these animals in the study, breeding soundness examination was performed according to the guidelines of CBRA (2013) on D-7 and D0 (seven days before and on the day of ivermectin administration, respectively). Fourteen individuals (n=14) that presented satisfactory results on breeding soundness evaluation were selected. On D0, immediately after semen and blood collection 800μg/Kg ivermectin 4% (Master LP , Ouro Fino , Cravinhos, Brazil) were administered subcutaneously. On D-7, D0, D7, D14, D21 and D63, immediate macroscopic and microscopic examination of semen samples were performed on the farm, and mediate examinations (concentration and spermatic morphology) were performed on the Animal Reproduction Laboratory, Federal University of Mato Grosso, Sinop, Brazil. Motility (P=0.068), mass movement (P=0.05) and concentration (P=0.073) on D7, D14, D21 and D42 were significantly different from D-7 and D0. During this study, the team of researchers noticed that on D63 there was a tendency to reestablish the values next to those observed on D-7. We could conclude that ivermectin 4% administration in Nellore bulls must be avoided during breeding season, because it induces temporary reduction in motility, in mass movement and in spermatic concentration.