Physiological and behavioral responses of dairy heifers in an integrated-crop-livestock-forestry system

The integrated crop-livestock-forestry system has been an option in tropics to mitigate the effects of heat stress on pasture-based system for dairy cows. We evaluate the effects of shade arrangements in integrated crop-livestock-forestry systems on physiological and behavioral responses of crossbred dairy heifers. Twenty-four crossbred European-Zebu heifers with 330.0±36.7 kg of body weight were assigned in three treatments: no shade, partial shade or total shade. Air temperature (34.4°C), black globe temperature (41.6°C), temperature humidity index (84) and heat load index (98) were higher (P<0.05) for the No shade treatment. Higher values of respiratory rate (99 mov.min-1) and skin temperature (38.1°C) were also found for the no shade treatment. Shade availability affected the grazing time (U = 246.5, P<0.05). Heifers spent 10% more time in pasture on shade treatments. No difference was found on time spent in rumination, drinking or walking on shade treatments. Shade provision was an efficient strategy to reduce respiratory rate and skin temperature as well as to increase grazing time in integrated crop-livestock-forestry system.   Key words: Cattle, Eucalyptus, heat stress, integrated farming, pasture, shade.