Physiological responses of Santa Inês x Dorper ewes and lambs to thermal environment of silvopasture and open pasture systems

Abstract The silvopasture is a sustainable livestock system, which has great potential for sheep, mainly focused on the thermal comfort and welfare of animals. However, there is a lack of information regarding the thermal environment and physiology of ewes and lambs raised in this system. This study was therefore aimed at assessing the influence of microclimate on the thermal comfort of postpartum ewes and lambs kept in silvopastoral (SP) or open pasture (OP) systems during the summer. Postpartum crossbred ewes (Santa Ines x Dorper; n = 24) and their lambs (n = 24) were randomly allocated to SP or OP group, being distributed into four paddocks per group (three ewes and three lambs per paddock). The microclimate characterization measured were dry-bulb ambient temperature (Ta, oC), black globe temperature (Tbg, oC), relative humidity (RH, %), grass temperature (Tg, oC) and wind speed (WS, m s−1). These variables were then applied to calculate the temperature and humidity index (THI), black globe temperature and humidity index (BGHI), and radiant heat load (RHL). To assess the thermophysiology response, the respiratory rate (RR, breaths min−1), heart rate (HR, beat min−1), rectal temperature (RT, oC), and hair coat surface temperature (ST, oC) were analyzed. Regarding the microclimate variables, Ta and Tg were higher in OP than in SP (P = 0.008 and P