Índices de conforto térmico e respostas fisiológicas de bezerros da raça holandesa em bezerreiros individuais com diferentes coberturas Thermal comfort indexes and physiological responses of holstein calves in individual houses with different roofings

Este trabalho avaliou a eficiência de abrigos para bezerros, a partir de índices de conforto térmico (carga térmica radiante, índice de temperatura de globo e umidade e índice de globo negro), pela comparação entre abrigos cobertos por telha de cimento-amianto e telha de cimento- celulose. O experimento foi implantado num sistema de abrigos convencionais, tipo boxe, com cinco tratamentos: telhados de cimento-amianto, cimento-celulose, cimento-celulose pintado de branco e telhado duplo de cimento-celulose, todos expostos ao sol, e telhado de cimento-celulose em área sombreada. Foram realizadas cinco repetições (um bezerro por repetição), de setembro a novembro de 2002, em Pirassununga - SP. As variáveis fisiológicas registradas foram freqüência respiratória e temperatura retal. Os abrigos expostos ao sol e com telha de cimento-amianto apresentaram os índices menos satisfatórios quanto ao conforto térmico animal, em relação aos demais abrigos ao sol. Os abrigos com telhas de cimento-celulose e em área sombreada apresentaram os melhores índices de conforto térmico animal. Os resultados das variáveis fisiológicas foram melhores para o tratamento posicionado à sombra. Encontrou-se relação entre os resultados de conforto térmico e os fisiológicos, em especial para a freqüência respiratória.<br>This work was focused in the efficiency of housing for calves, based on thermal comfort indexes (radiant thermal load, black globe humidity index and black globe index). It was compared animal housing covered with commercial corrugated sheets produced with asbestos cement and cellulose cement tiles. The experiment was carried out in a system of conventional housing, box type, with five treatments: roofs with asbestos cement tiles, cellulose cement tiles, cellulose cement painted tiles and double layer of cement cellulose tiles, all of them exposed to the sunlight and cement cellulose roof under shade. The experiment involved five replications (one calf per replication), during the spring time of 2002, in Pirassununga, State of São Paulo, Brazil. Physiological variables of thermoregulation (respiration rate and rectal temperature) were registered. The housing directly exposed to the sunlight and covered with asbestos cement sheets presented the less satisfactory results for the animal thermal comfort in comparison with the other treatments also exposed to the sun. The housing covered with cellulose cement tiles under shade showed the best results of thermal comfort. The results of the physiological variables were significantly better for the treatment positioned under shade. A satisfactory relation between the thermal comfort indexes and the physiological results (especially respiration rate) were found for the conditions of the present work

Influence of the outer skin on the flexural properties and thermal conductivity of densified Dendrocalamus asper bamboo

In this work, the effect of densification and the maintenance of the outer skin on the flexural properties and thermal conductivity of Dendrocalamus asper Backer ex K.Heyne bamboo was investigated. The results showed improvements in bending resistance for the densified samples compared to the un-densified bamboo. Densified samples with the outer skin showed the highest bending strength. Samples with the outer culm wall in compression offered the best results, with an average modulus of rupture (MOR) of around 348.9 MPa and modulus of elasticity (MOE) of 28.4 GPa. These values are around 40% and 86% (MOR), and 17% and 30% (MOE) higher compared to densified samples without the skin and un-densified samples, respectively. The fracture sections of specimens after bending tests were analyzed using Scanning Electron Microscopy (SEM) to visualize crack propagation within the outer skin and bamboo tissues. Maintaining the skin increases the thermal conductivity, and the densified bamboo with the skin has a thermal conductivity of around 0.23 W/m.K, 12.8% higher than the densified bamboo without skin and 22.5% higher than un-densified bamboo. Although a reduction in thermal performance was achieved, it was concluded that is reasonable to keep the bamboo skin, as it improves the overall mechanical resistance and reduces material loss during bamboo processing