Eficiência térmica de materiais utilizados na cobertura de abrigos individuais para bezerras Girolando

Abstract

The present study was developed with the aim to evaluate the thermal efficiency and comfort level provided by different covering materials from individual housings for Girolando calves and their effects on animal performance. The experiment was carried out on a commercial farm which produces queijo de coalho (a kind of curd), Várzea Alegre Farm, in the municipaluty of Pesqueira, State of Pernambuco, latitude 8º17’10” S, longitude 36º 53’03” O and altitude of 800 m. .The experiment was carried from January to March of 2012, lasting for 56 days, on 24 crossbred calves with genetic composition of 7/8 Holstein-Gir. The treatments were composed of three types of covering materials, palm straw, recycled polymer tile and asbestos cement tile. It was adopted a completely randomized design, and in order to compare means it was used the Tukey test (p<0.05). Results showed that there has been significant difference among the studied treatments, in which recycled-tile-covered housings presented lower values of mean termperature on the superior surface throughout the experiment, being the maximum value found around 36.9 °C and the minimum of 14.4 °C. Bioclimatic evaluation pointed out a significant effect for enthalpy and radiant thermal load, and recycled-tile-covered housings have presented the best values, around 59.3 kJ kg dry air-1 and 444.8 W m-2, respectively. For physiological variables and animal performance there has not been a significant difference among any studied variables, however, the respiratory frequency in all treatments has been above stablished thresholds for thermal comfort, being the most emphasized for animals housed under asbestos-cement-covered hutches, which was 57.2 mov. min-1, but this mechanism was capable of maintaining the rectal temperature within normal thresholds.