Resistance of cattle to the tick Boophilus microplus. I. Artificial infestation

Abstract

The resistance of the Canchim cattle to the cattle tick Boophilus microplus (Canestrini), as compared to the Nelore cattle, was evaluated through artificial infestation. Sixty animals (30 males and 30 females), half of each breed, were artificially infested on two occasions, fourteen days apart, with 20,000 larvae, to assess tick resistance. Eighteen days after each infestation, three counts of the number of female engorged ticks at one side of the animals were performed at alternate days. The data were analyzed as the percentage return (PR = percentage of ticks counted in relation to the total number infested), transformed into (PR)1/4. The results indicated a highly significant (P<0.01) sex effect, with the females (PR = 0.2740%) showing higher resistance than males (PR = 0.6439%). The Nelore animals (PR = 0.0989%) were more resistant (P< 0,01) than the Canchim ones (PR = 1.2544%). However, the Canchirn breed can be considered as having good resistance, as shown by the low percentage return and a high percentage (93.3%) of the animals showing tick mortality rate above 95%. It was also shown, for the Canchim cattle only, that the light-colored animals were more resistant.