A dinâmica de queda de fêmeas ingurgitadas do carrapato Boophilus microplus foi avaliada na Estação Experimental da Embrapa Gado de Leite, em Coronel Pacheco- MG, Brasil. O objetivo foi avaliar as vantagens da modificação do horário de ordenha dos bovinos, considerando a higienização do pasto, em relação ao carrapato. O experimento constou de uma fase de verão/outono e uma de inverno, para testar diferenças no ritmo de queda dos carrapatos entre as duas estações. Os resultados mostraram diferenças significativas entre as fases. No verão/outono, as fêmeas ingurgitadas apresentaram maior porcentagem de queda entre 7 e 10 horas (35,3%) e no inverno entre 6 e 9 horas (19,69%) e entre 14 e 17 horas (21,79%). A porcentagem de queda de fêmeas ingurgitadas no período foi de 35,15% para o sistema de ordenha de 5-8h e 13-16h e de 45,48% para o sistema de ordenha de 8-11h e 16-19h, durante os meses de verão/outono. Nos meses de inverno, o porcentual de queda foi de 40,51% e de 32,71% para os dois horários de ordenha respectivamente. Considerando o tempo que os animais permanecem estabulados para a suplementação no cocho durante o período entre as ordenhas na época seca do ano na região (maio a setembro), a porcentagem de queda de fêmeas ingurgitadas foi de 55,83% para o sistema de ordenha de 5 a 16h e de 52,36% para o sistema de ordenha de 8 a 19h.

A description of the drop-off behaviour of engorged females of the tick Boophilus microplus was carried out as a result of an experiment at the Experimental Station, Embrapa Gado de Leite, Coronel Pacheco, MG, Brazil. Its objective was to evaluate any repercussions of changing the time of milking of cattle in terms of reduced recontamination of the pastures with the tick. Such possible changes in this daily cattle management routine have recently become a reality since the advent of refrigerated on-farm storage of the milk and non-daily collection by tanker truck. The field experiment consisted of a phase in summer, with a longer photoperiod, and in winter, with a shorter photoperiod. Twelve weekly experimental repetitions, of 24 hours duration, were carried out in each of these seasons. For each repetition, eight non-lactating, 7/8 Holstein-Friesian x Zebu cows, naturally infested with B. microplus and maintained on pastures, were removed to an experimental area on the day in which the observations were to be made and maintained in individual stalls. At each hour, over 24 hours, all fully engorged ticks that had dropped off naturally from the cattle were collected from the stalls. The results showed a significant difference in the rhythm of their drop-off in the summer compared to winter. In the summer the greater proportion of ticks dropped off between 07 and 10 (35.3%) with a maximum at 09. In winter, there were two daily periods of greater drop-off of ticks, the first between 06 and 09 (19.69%) with a maximum at 06, and the second between 14 and 17 (21.79%) with a maximum at 15. The percentage of ticks dropping off during the traditional milking time (05-08 and 13-16) would have been 35.15%, while those falling during an alternative sytem under consideration for Central Brazil (08-11 and 16-19) would be 45.48%, during the summer. During the winter, the proportion of ticks falling from the cattle is 40.51% and 32.71% for the two times of milking, respectively. Considering the time that the animals remain in stalls for feed supplement during the period between milkings during the dry season (May to September), the proportion of ticks falling would be 55.83% for the traditional system (05-16) and 52.36% for the milking period under consideration (08-19).