A comparison of cattle tick control by pasture spelling, planned dipping, and tick-resistant cattle

Abstract

Control of Boophilus microplus by pasture spelling, planned dipping, and simulated "conventional" control methods was compared in duplicate herds of British cattle, and by simulated "conventional" control methods in duplicate herds of Zebu x British and a single mixed herd of Zebu x British and British cattle. Herds under conventional control were treated with an acaricide (dipped) when the count of "standard" ticks (5 mm or more in length) on the right side averaged 20 or more per animal. Herds under pasture spelling grazed alternately in two adjacent paddocks; the summer spelling period was 3½ months, followed by spelling periods of 4½ months, and cattle were dipped on transfer between paddocks. Herds under planned dipping were dipped at 21-day intervals until few larvae remained on the pasture, this treatment being repeated when the count of standard ticks averaged more than 20 per animal.

Observations over 2 years confirmed the results of an earlier experiment which showed that pasture spelling and planned dipping resulted in increased efficiency of tick control. Compared with British herds under conventional control which required dipping on 19 and 20 occasions, herds managed by pasture spelling were dipped only on seven occasions and showed a mean reduction of 81% in tick burden. Herds subjected to planned dipping required 18 treatments but the tick burden was reduced by 83%. The two Zebu x British herds required dipping on four and 10 occasions and showed a mean reduction in tick burden of 39% compared with British herds under conventional control. There was little improvement in tick control in the mixed herd of Zebu x British and British cattle.

Assessment of the tick resistance status of the Zebu x British cattle by artificial infestation with known numbers of larvae showed that the survival to mature female ticks was 1.3 and 1.8% for the herds requiring four and 10 acaricidal treatments respectively in the wet tropics. In a similar assessment of the "resistant" Australian lllawarra Shorthorn (AIS) cattle herds which required one treatment or none over a tick season in southern Queensland (Wilkinson 1962) the survival was 4.4 and 5.2% respectively. The mean survival of female ticks to maturity on individual Zebu x British cattle was 1.4% (range 0.01–6.6%) compared with 8.1 % (0.2–27.4%%) for AIS cattle.