Índices de conforto térmico, fisiológicos e desempenho de bovinos mestiços confinados com sombreamento natural e artificial.

Abstract

The beef cattle industry is a relevant activity in Brazil, which has the largest commercial herd in the world. The search for techniques able to minimize the stress caused by climatic effects becomes necessary to improve the physiological conditions of the herd and alter the behavior of food and water intake, increasing the performance of the animals both for beef and milk. Shading can be used as a management tool to minimize thermal stress in cattle. The damages caused by the climate, especially by heat stress, will become even more worrisome in the future, due to the notorious effects of global warming, which has threatened the agricultural production systems. This study aimed to evaluate which type of shading would provide better thermal comfort indexes, through animals’ physiological responses, for cattle raised in a confinement system and, consequently, for gain in meat production. It was carried out at the Passagens farm, located in the municipality of Itatuba, Paraíba State, Brazil. Thirty crossbred Nelore cattle were selected and divided into six pens. The treatments consisted of full sun, artificial shade using sombrite, and shade of trees. During the experiment, the following environmental variables we collected: ambient temperature, relative humidity, black globe temperature, and wind speed (m s-1). Subsequently, the Black Globe Temperature and Humidity Index (BGHI) and Radiation Thermal Charge Index were calculated. Respiratory rate, surface temperatures, and rectal temperature physiological variables were collected. The environments with artificial and natural shade showed significant improvements (P<0.05) in the environmental variables and thermal comfort indexes, reflecting positively on the productive index (weight gain). The BGHI presented the highest correlation with the physiological variables, with most values above 84, which is considered as an EMERGENCY case, regarding animal welfare, but being already in ALERT in the first hours of the day, in all treatments. The animals submitted to the Tree treatment presented a higher weight gain (10.1% higher) than the other ones. The animals with access to natural shade achieved slaughter weight at 52 days. Thus, shade becomes a good alternative to increase meat production in confinement and especially makes better the environment in which animals are reared.