Physiological responses of dairy cows as a function of environment in holding pen

Abstract

This research aimed to assess the climatization configuration in a holding pen for dairy cattle considering physiological responses of animals and thermal comfort indexes. Experimental design consisted of 16 cows in a Latin square design containing four groups of four animals (G1, G2, G3 and G4) and four periods (P1, P2, P3 and P4), in which four environments were used as treatments: EXT - external environment (control); SHA - shading with polypropylene mesh, 80% light interception; S+S - shading and water sprinkling; and S+S+V - shading, sprinkling and ventilation. Dry and wet bulb temperature, black globe temperature, wind speed and humidity were recorded during the climatization process, between October 13 and December 7. Subsequently, temperature-humidity index (THI), black globe temperature and humidity index (BGTHI), radiant heat load (RHL) and heat load index (HLI) were calculated. After climatization, respiratory rate (RR), surface temperature (ST), and rectal temperature (RT) were recorded. Animals submitted to EXT presented physiological responses that indicated heat stress. The best physiological response was found in S+S+V, which reduced RR by 58.6% when compared to the other environments.