SILVA, Ana Mary .da; ALENCAR, Mauricio Mello de.; REGITANO, Luciana Correia de Almeida.; OLIVEIRA, Márcia Cristina de Sena.
Resumo:
It was evaluated in this work, the degree of natural infestation by external parasites in beef cattle females
from three genetic groups. Countings of cattle tick (Rhipicephalus (Boophilus) microplus), horn fly (Haematobia irritans)
and beef-worm (Dermatobia hominis) were performed from July 2003 to December 2004 in females from the genetic groups
Nellore (NE), Angus × Nellore (AN), Canchim × Nellore (CN), and Simmental × Nellore (SN) naturally infested. It was realized
from 6 to 10 countings in each animal, totalizing 5,384 observations in females at seven physiological stages (calf; empty
heifers, pregnant heifers, primiparous cows with or without calf; and pluriparous cows, with or without calf). Data, which were
transformed by log10 (n + 1), were analyzed by the least square method with a statistical model that included effects of the
female genetic group, of the animal within a genetic group (error a), year-season counting, physiological state, and year-season
× genetic group interaction. Differences among genetic groups depended on year-season counting; however, in general, Nellore
females were the least infected by ticks, and Angus × Nellore females were the most infected by horn flies and by beef-worms.
There was a physiological stage effect of the female in all the three studied characteristics and the differences changed
accordingly to the trait. Despite of the counting year-season × genetic group, there are differences among Nellore, Canchim
× Nelore, Angus × Nellore and Simmental × Nelore genetic groups regarded to the degree of natural infestation by cattle tick,
horn fly and beef-worm.