The dynamics of Boophilus microplus infestation on 20 crossbred heifers under intensively grazing elephant grass pastures was studied during two years. The animals were divided into two groups: heifers in one group (treated group) received acaricide treatments with doramectin during the course of the study. Animals were weighted every six months. The infestation curves observed on treated and control groups showed similar patterns, with peaks of parasitism in the same period. The lowest parasitic burdens occurred during winter months (dry season). In spring early rainy seasons there was a peak of infestation, followed by another in February (late rainy season). Near the end of autumn, tick burdens dropped naturally. The dynamics of tick burdens was not statistically associated with any of the climatic variables analysed (P>0.05). No differences among mean live weights of heifer groups at any of the five weighting periods (P>0.05) were observed. Peaks of engorged females were associated with dropping of hemoglobin levels in heifers (P<0.01). The dynamics of B. microplus infestation on cattle under intensively grazing elephant grass was similar to other studies conducted under conventional grazing.
Cattle; Boophilus microplus; tick; intensive grazing
