Rhipicephalus microplus infestation level and its association with climatological factors and weight gain in Bos taurus x Bos indicus cattle

Tick infestation is an ongoing challenge in cattle production, but chemical control methods can pose a risk to both animals and handlers. An evaluation was done of natural Rhipicephalus microplus infestation, its correlation to climatological factors and its effect on weight gain in dual-purpose cattle. Individuals consisted of 31 Bos taurus x Bos indicus cattle of both sexes with an average age of 307 d. Every 28 d for 15 mo, counts of semi-engorged ticks (4.5 to 8.0 mm in diameter) were done and the animals weighed. Tick counts were done from the head to the base of the tail, including the fore and hind limbs, and the ventral region. Response variables were tick count and average weight per animal. Average tick count per animal was higher (P<0.05) in the hottest month (July) than in the other months. Calf's sex and breed group had no effect (P>0.05) on tick count. Individual weight gain decreased 34 g (P<0.05) for each semi-engorged tick per 28-day period. Tick count had a low correlation (P<0.01) with environmental temperature and relative humidity, but average weight gain was negatively and moderately correlated with tick count (-0.67; P<0.01). Animals with a high infestation level (61+ ticks) exhibited lower average weight gain (P=0.001) than those with a medium (31 to 60 ticks) or low level (0 to 30 ticks). Boophilus microplus infestation in dual-purpose cattle requires stricter control during high-temperature months (April to July).