This study evaluated the repellent activity of the botanical compounds thymol, carvacrol, nootkatone, and eugenol (5%), as well as the combination of 2.5% nootkatone + 2.5% eugenol, against Amblyomma sculptum nymphs under laboratory and field conditions. In contact bioassays, carvacrol and nootkatone showed the highest mean repellency rates (94.5% and 93.7%), followed by thymol and eugenol (90.2% and 87.2%). The combination (nootkatone + eugenol) resulted in 92.8% repellency, with 100% efficacy in some evaluation periods. The repellency of 7% DEET (positive control) was 82.2%. Nootkatone 5% and the combination (nootkatone + eugenol) were also tested in a Y-tube olfactometer, showing repellency rates of 86.1% and 72.2%, respectively, both higher than 7% DEET (69.4%). In field trials, volunteers wore treated socks and walked through an area naturally infested with nymphs. A significant reduction (p < 0.05) in tick counts was observed in the treated groups (about five unfed nymphs) compared to the control (about 40 unfed nymphs). Cumulative efficacy exceeded 85% in both treatments. In the cost simulation, the estimated cost of a 100 mL formulation containing 5% nootkatone was USD 50.8, while the combination (nootkatone + eugenol) presented a cost USD 28.6, representing a 44% reduction with no loss of efficacy in field conditions. These results indicate that all compounds tested showed repellent activity in the laboratory. Nootkatone has high repellent activity, and its combination with eugenol is a promising and more economically viable alternative for tick repellency.

This study evaluated the repellent activity of DEET, eugenol, methyl eugenol, 1,8-cineole, and their combinations against Amblyomma sculptum nymphs through laboratory and field tests. Initially, the botanical compounds were tested individually in Petri dish assays to assess repellent activity over various intervals (1 min to 168 h) at concentrations of 2%. Eugenol and methyl eugenol exhibited the highest average repellent percentages (60 to 90%), with significant effects (p < 0.05) across most evaluation periods, in contrast to 1,8-cineole. Therefore, eugenol and methyl eugenol were selected for combination testing with DEET. The combinations of 7% DEET + 1% eugenol and 7% DEET + 2% methyl eugenol showed the best results, with average repellent efficacy exceeding 85%. The first combination was selected for field evaluation. In this test, volunteers wore treated socks and walked for two hours in a naturally infested area. A significant reduction (p < 0.05) in the number of ticks recovered from the socks was observed in the 7% DEET and 7% DEET + 1% eugenol treatments, with efficacies of 82.5% and 88.5%, respectively, after 120 min. Isolated eugenol showed limited field efficacy, with significant repellent activity (p < 0.05) lasting only 20 min. The results highlight the potential of eugenol and methyl eugenol as repellent compounds, especially when combined with DEET. The field study confirmed the efficacy of the 7% DEET + 1% eugenol.

Growth and carcass traits are essential selection criteria for beef cattle breeding programs. However, it is necessary to combine these measurements with body composition traits to meet the demand of the consumer market. This study aimed to estimate the genetic parameters for visual scores, growth (pre and post-weaning weights), and carcass (rib eye area (REA), back and rump fat thickness) traits in Nellore cattle using Bayesian inference. Data from 12,060 animals belonging to the HoRa Hofig Ramos herd were used. Morphological traits were evaluated by the MERCOS methodology. The heritability estimates obtained ranged from low to high magnitude, from 0.15 to 0.28 for visual scores, 0.13 to 0.44 for growth, and from 0.42 to 0.46 for carcass traits. Genetic correlations between visual scores and growth traits were generally of moderate to high magnitudes, however, visual scores showed low correlations with carcass traits, except between sacral bone and structure and REA. Selection for visual score traits can lead to favorable responses in body weight and vice versa, but the same is not true for carcass traits. Morphological categorical traits can be used as complementary tools that add value to selection.

Background: Fluralaner has been used in the strategic control of the Rhipicephalus microplus tick, an important ectoparasite for cattle farming. However, the effects of its application on the susceptibility profiles of these tick populations after treatment have not yet been investigated. In this study, we evaluated the effect of a strategic control protocol with fluralaner on the phenotypic susceptibility profile of a population of R. microplus before and after its implementation. Methods: Thirty naturally infested cattle were divided into two experimental groups: T01 (control group): cattle treated with a topical (spray) formulation containing a synthetic pyrethroid and two organophosphates; T02 (strategic control): cattle treated with a formulation (pour-on) containing only fluralaner. For group T01, animals were treated when the average tick count was ≥30 to allow determination of the infestation challenge on the farm, while animals in group T02 were treated when 30% of the animals had adult ticks < 4 mm. Tick counts on animals were performed every 7 days for 266 days. Larvae monitoring in the pasture was performed every 30 days using a dragging flannel for 240 days. Larval immersion tests (LIT) and adult immersion tests (AIT) were used to assess the phenotypic susceptibility profile of ticks before and after the implementation of the strategic control protocol over a tick season in a tropical region. Results: The animals in the group treated with fluralaner (T02) had lower mean tick counts ( p ≤ 0.05) than those observed in the control group (T01) in 35 of the 38 evaluations during the 266 days of the study. In the pasture, the number of larvae in T02 was lower ( p < 0.05) in seven of the eight evaluations. There was no increase in LC50 values for larvae and engorged females after using the strategic control protocol with fluralaner for 9 months. Conclusions: The use of the strategic control protocol with fluralaner resulted in a significant reduction in tick numbers on cattle and in pastures, and after 1 year of use, the population remained susceptible to this compound. No upward trend in LC50 values was observed after 9 months of fluralaner use.