Spatiotemporal variations on infrared temperature as a thermal comfort indicator for cattle under agroforestry systems.

With the expanding use of thermal assessment techniques in beef cattle, infrared thermography has become a promising tool for assessing the environment for animal thermal comfort. Goals of this study were: (1) to evaluate cattle thermal comfort in agroforestry systems with different shade availability (2) to verify the spatiotemporal variations of infrared temperature inside agroforestry systems, and; (3) to test infrared thermography as a potential tool to assess animal thermal comfort indices in agroforestry systems. A trial was carried out between June 2015 and February 2016, covering Central-Brazil's dry winter and rainy summer seasons, respectively. The experimental area of Embrapa Beef Cattle is located in Campo Grande (Mato Grosso do Sul), coordinates 20°24'53″ S, 54°42'26″ W and 558 m altitude. The 12 ha plot has two agroforestry systems varying shade availability. Traditional Black Globe Temperature and Humidity Index, Heat Load Index and Radiation Thermal Load were determined, from measurements using digital thermo-hygrometers, with datalogger. Surface temperature and humidity of tree canopies and pasture were determined using an infrared thermographic camera. Results show spatiotemporal variations in infrared temperature. This means that the environment inside agroforestry systems is not homogeneously comfortable for cattle, and the system with the lowest shade availability has the greatest heat accumulation area. Weak to strong associations were identified between infrared variables and thermal comfort indices (0.08 = r ≤ 0.75). Positive relationships were also obtained and equally well explained by the Black Globe Temperature and Humidity Index and Heat Load Index (0.55 = R2 ≤ 0.94). We conclude that infrared thermography can be used as a tool to assess thermal comfort indices in agroforestry systems and to determine onset of animal thermal stress from environment and heat body accumulation.

Shading effect on microclimate and thermal comfort indexes in integrated crop-livestock-forest systems in the Brazilian Midwest.

The objective of this paper was to perform a microclimate evaluation and determine the indexes of thermal comfort indexes, in sun and shade, in integrated crop-livestock-forest systems with different arrangements of eucalyptus and native trees, in the Brazilian Midwest. The experiment was conducted at Embrapa Beef Cattle in Campo Grande, state of Mato Grosso do Sul, Brazil, from July to September 2013. The evaluations were conducted on four consecutive days, from 8:00 a.m. to 5:00 p.m., local time (GMT -4:00), with 1 hour intervals, recording the microclimate parameters: air temperature (°C), black globe temperature (°C), wet bulb temperature (°C), relative humidity (%), and wind speed (m.s-1), for the subsequent calculation of the Temperature and Humidity Index, the Black Globe Temperature and Humidity Index, and the Radiant Thermal Load. The largest changes in microclimate parameters were found in the full sun, between 12:00 p.m. and 1:00 p.m., in less dense eucalyptus system, followed by the scattered native trees system, resulting in a maximum Temperature and Humidity Index of 81, Black Globe Temperature and Humidity Index of 88 and Radiant Thermal Load of 794 W m-2. Therefore, it is observed that with the presence of trees in pastures were possible reductions of up to 3.7 % in Temperature and Humidity Index, 10.2 % in the Black Globe Temperature and Humidity Index, and 28.3 % of the Radiant Thermal Load in the shade. Thus, one can conclude that the presence of trees and their arrangement in the systems provide better microclimate conditions and animal thermal comfort in pastures.

Infrared thermography for microclimate assessment in agroforestry systems.

In agroforestry systems, trees modify climatic parameters over a given area and create a complex microclimate through interactions between topography, plant composition and organizational structure of trees. In this way, indicators such as surface temperature of tree canopy and pasture, monitored by infrared thermography, are important to monitor the thermal environment of animal production and pasture establishment. Goals of this study were (1) to evaluate temporal and local variations of temperature and humidity leaf surface of tree canopy and pasture in agroforestry systems by infrared remote sensing and, (2) to validate infrared thermography as a potential tool for assessment microclimate in agroforestry systems. The study was carried out between June 2015 and February 2016 in an experimental area located at 54°370'W, 20°270'S and 530 m altitude, in Brazil. Surface temperatures and humidity of tree canopy and pasture in two agroforestry systems with different densities and tree spatial arrangements were determined using infrared thermography. Air, black globe and dew point temperatures, relative humidity and wind speed were measured using digital thermo-hygrometers with datalogger. Moderate to strong associations have been identified between microclimate parameters and those monitored by means of thermography measurements (0.45 ≥ r ≤ 0.78), suggesting positive relationships and equally well explained by air temperature, black globe temperature and relative air humidity (R2 = 0.68 ≥ R2 ≤ 0.98). Variations in hourly averages of temperatures and humidity of pasture and tree canopy show similar patterns between seasons, with consistently higheraverages during summer and under full sun, indicating the existence of a thermal band with leaf temperatures above air temperature. Therefore, this work's findings support use of infrared thermography as a tool for microclimate assessment in agroforestry systems.