Estimation of heat exchanges in Boer crossbred goats maintained in a climate chamber.

Exposure of goats to high air temperatures can induce physiological and behavioral adjustments, increasing the dissipation of excess body heat in the latent form, and intensification of the use of these thermoregulatory tools can result in physiological and productive damage to animals. With this, the objective of the research was to quantify the levels of thermal stress and the sensible and latent heat losses of Boer crossbred goats submitted to different air temperatures, in a climatic chamber. Six male crossbred goats of the Boer breed, with an average weight of 25.06 ± 4.43 kg and mean age of six months, were grouped using a completely randomized design, with three treatments (air temperatures of the 26, 30 and 34 °C, respectively) and six replicates (animals) with 68% relative humidity. The temperature and relative humidity of the air were collected to calculate the temperature and humidity index (THI) and heat exchanges. Were collected the physiological responses rectal temperature (RT) and surface (ST) and respiratory rate (RF), with these data were estimated the heat exchanges by radiation (L), convection (Cr), total sensitive (Gs), latent of the respiratory tract (Er), cutaneous (Ec), total latent (Et) and total heat exchange (Wt). It was found that the THI values were classified as thermal comfort, moderate stress and very stressful, respectively, in the three conditions evaluated. With the increase in AT, the animals significantly increased (P < 0.05) the RT, ST and RF, and consequently reduced sensitive heat exchanges, from 38 to 8%, and increased latent heat exchanges, from 62 to 92%, when compared air temperatures of 26 and 34 °C, respectively. Physiological responses showed a significant negative (P < 0.05) correlation with sensitive heat exchanges and a positive correlation with latent heat exchanges. In very stressful thermal conditions, the animals lost almost all of the excess metabolic heat by latent means (skin and respiratory tract).

Mapeamento e quantificação de parâmetros biofísicos e radiação líquida em área de algodoeiro irrigado / Mapping and quantification of biophysical parameters and net radiation over irrigated cotton fields

O sensoriamento remoto tem se mostrado eficaz na avaliação de fluxos de energia e de propriedades biofísicas de superfícies vegetadas em escala regional. No presente trabalho, utilizou-se o algoritmo SEBAL - Surface Energy Balance Algorithm for Land e imagens TM - Landsat 5 para mapeamento e quantificação do albedo (α), NDVI, temperatura da superfície (Ts) e radiação líquida (Rn) em área de algodão irrigado por pivô central, na Fazenda Busato (13,25º S; 43,42º W; 436 m), município de Bom Jesus da Lapa, Bahia. Seis imagens de céu limpo ao longo do período da cultura (janeiro a agosto de 2007) e os respectivos dados meteorológicos foram utilizados para implementação do algoritmo. Após o processamento digital das imagens, verificou-se nítida relação dos parâmetros α, Ts e NDVI com o desenvolvimento da cultura. Os menores valores de α (10 a 20 por cento) e Ts (< 24ºC) e os maiores de NDVI (>0,75) ocorreram na fase de máxima cobertura do solo. A radiação líquida (Rn) diminuiu progressivamente com o tempo, influenciada, principalmente, pela diminuição da radiação solar incidente com o aumento do ângulo zenital. Os valores de Rn variaram de 430 W m-2 a 700 W m-2 nos pivos cultivados. A técnica de sensoriamento empregada capturou de forma nítida a variabilidade temporal e espacial de Rn e dos parâmetros biofísicos, cujos valores encontrados são compatíveis com os reportados na literatura para a mesma cultura sob regime de irrigação.

Remote sensing is currently an important tool for evaluation of net radiation and biophysical parameters over vegetated surfaces on a regional scale. In this research, the SEBAL - Surface Energy Balance Algorithm for Land and TM - Landsat 5 images were used to map and quantify the albedo (α), NDVI, surface temperature (Ts) and net radiation (Rn) of center-pivot irrigated cotton fields in the Busato Farm (13.25º S; 43.42º W; 436 m asl), western of State of Bahia, Brazil. Images from six clear-sky days during the cropping season (January to August 2007) and the corresponding meteorological data were used to run SEBAL. Results showed a clear relationship between α, NDVI, and Ts and crop development. The lowest values of α (10 to 20 percent) and Ts (< 24ºC), as well as the highest values of NDVI (> 0.75), occurred at the time of maximum ground cover. Net radiation decreased progressively with time, following the decrease of the incident solar radiation with increasing solar zenith angle. In the cropped center pivots, Rn ranged from 430 Wm-2 to 700 Wm-2. The remote sensing technique used in this study was consistent in capturing the temporal and spatial variability of the biophysical parameters and net radiation over the irrigated cotton, and their values are in agreement with those reported in the literature for the same crop in irrigated areas.