THI: Is it a Reliable Measure to Assess Cattle Thermal Stress in Silvopastoral Systems in a Subtropical/Temperate climate?

Abstract

Livestock performance and welfare may be adversely affected by weather conditions, heat stress being a sign of deterioration of animal welfare. Signs like respiration rate (RR), body temperature, changes of physiological and metabolic parameters amongst others, are considered as indicators of heat stress in cattle. The temperature humidity index (THI) is commonly used as an indirect indicator of the levels of heat stress in cattle. Aiming to characterize this effect, we registered panting in European beef cattle allocated either in Silvopastoral Systems (SPS) or in open pasture (OP). THI scores were registered during the hottest month (January) in extensive farms in Uruguay with two pairs of sensors (I-button "Hygrochron" DS1923) installed in all paddocks to register ambient temperature and humidity. THI values were over the alert and emergency levels for both OP and SPS, nevertheless the THI values for SPS were higher. No animal panting was recorded during the observation period. This fact suggested that THI should be complemented with other environmental measures to better reflect the thermal stress in cattle in SPS in subtropical/ temperate climate.