Ecological aspects of the free-living ticks (Acari: Ixodidae) on animal trails within Atlantic rainforest in south-eastern Brazil

In a recent ecological study of the ticks on animal trails within an area of Atlantic rainforest in south-eastern Brazil, Amblyomma aureolatum, A. brasiliense, A. incisum, A. ovale and Haemaphysalis juxtakochi were found questing on the vegetation. Most of the ticks recorded by a small, man-made dam on the forest border were A. dubitatum but a few A. brasiliense and A. cajennense, one A. incisum and one H. juxtakochi were also found. The seasonal activity of the ticks indicated that A. incisum and A. brasiliense had one generation/year. On the animal trails, most tick species and stages quested on the vegetation at a height of 30-40 cm above ground level. The questing larvae and adults of A. incisum tended to be found higher, however, with the greatest numbers recorded 40-50 cm (larvae) or 60-70 cm (adults) above ground level. Most of the adult ticks (81.1% -100%), nymphs (78.6%-100%) and larval clusters (100%) found on a forest trail remained questing at the same location over a 24-h period. Carbon-dioxide traps in the rainforest attracted, 50% of the ticks observed questing on the nearby vegetation and, curiously, the CO(2) traps set deep in the forest attracted far fewer ticks than similar traps set by the dam. The ecological relationships between the ticks, their hosts and the rainforest environment are discussed.

Genotype effects on body temperature in dairy cows under grazing conditions in a hot climate including evidence for heterosis

We compared diurnal patterns of vaginal temperature in lactating cows under grazing conditions to evaluate genotype effects on body temperature regulation. Genotypes evaluated were Holstein, Jersey, Jersey x Holstein and Swedish Red x Holstein. The comparison of Holstein and Jersey versus Jersey x Holstein provided a test of whether heterosis effects body temperature regulation. Cows were fitted with intravaginal temperature recording devices that measured vaginal temperature every 15 min for 7 days. Vaginal temperature was affected by time of day (P < 0.0001) and genotype x time (P < 0.0001) regardless of whether days in milk and milk yield were used as covariates. Additional analyses indicated that the Swedish Red x Holstein had a different pattern of vaginal temperatures than the other three genotypes (Swedish Red x Holstein vs others x time; P < 0.0001) and that Holstein and Jersey had a different pattern than Jersey x Holstein [(Holstein + Jersey vs Jersey x Holstein) x time, P < 0.0001]. However, Holstein had a similar pattern to Jersey [(Holstein vs Jersey) x time, P > 0.10]. These genotype x time interactions reflect two effects. First, Swedish Red x Holstein had higher vaginal temperatures than the other genotypes in the late morning and afternoon but not after the evening milking. Secondly, Jersey x Holstein had lower vaginal temperatures than other genotypes in the late morning and afternoon and again in the late night and early morning. Results point out that there are effects of specific genotypes and evidence for heterosis on regulation of body temperature of lactating cows maintained under grazing conditions and suggest that genetic improvement for thermotolerance through breed choice or genetic selection is possible.