THE EFFECT OF CATTLE TICK (BOOPHILUS MICROPLUS) ON PREGNANT AND LACTATING BRAHMAN-CROSS AND BRITISH-BREED COWS IN NORTHERN AUSTRALIA

Natural infestations of cattle tick (Boaphilus microplus) on breeding Hereford, Shorthorn and Brahman-cross cows were observed in a dry tropical environment. Herefords were dipped three times and Shorthorns four times during a 12 month period, while the Brahman-cross cattle were dipped twice during a 3-year period. No differences in tick infestations could be shown between pregnant and non-pregnant or lactating and non-lactating cows even though they were under severe nutritional stress. No consistent negative correlations were shown between body- weight changes and tick counts. This was probably due to the effect of dipping in the Herefords and Shorthorns. There was a trend towards significant negative correlations in July and August over each of three years for undipped Brahman-cross cows. Some form of tick control on breeding Brahman-cross cows, aimed at reducing tick burdens during July to September may be beneficial in the environment under study.