Abstract
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.
Highlights
In tropical regions, an almost constant occurrence of temperatures above the thermoneutral environment of dairy cattle is predominant, with values ranging from 0 to 16 °C (PEREIRA, 2005)
The best physiological response was found in S+S+V, which reduced respiratory rate (RR) by 58.6% when compared to the other environments
Average air temperature was 21.08 °C, not being necessary to turn on the climatization system, since the temperatures were lower than 26 °C during this period
Summary
An almost constant occurrence of temperatures above the thermoneutral environment of dairy cattle is predominant, with values ranging from 0 to 16 °C (PEREIRA, 2005). Climatization strategies began to be used aiming at reducing the effect of heat stress, which may reflect directly on improving animal productive performance (RODRIGUES et al, 2010; NASCIMENTO et al, 2013). In this context, holding pens or pre-milking parlors are critical points inside dairy properties because in these environments animals remain on average 15 to 75 min before entering the milking parlor. Water sprinkling is an important technique that aims to speed up heat exchange by the evaporation process (SCHÜTZ et al, 2011; CERUTTI et al, 2013)
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