Infrared Thermography to Evaluate Heat Tolerance in Different Genetic Groups of Lambs

Abstract

Heat stress is considered a limiting factor for sheep production. We used information from physiological characteristics linked to heat tolerance to determine whether infrared thermography temperatures were able to separate groups of animals and determine the most important variables in this differentiation. Forty-eight four-month-old male lambs from eight genetic groups were used. Physiological (rectal temperature–RT, heart rate–HR, respiratory rate–RR) and blood traits, infrared thermography temperatures, heat tolerance indices, body measurements, weight and carcass traits were measured. Statistical analyses included variance, correlations, factor, discrimination and regression. Observing the correlations between physiological characteristics (RT, RR and HR) with temperatures measured by infrared thermography, regions for further studies should include the mean temperature of flank, nose and rump. Results show that there are strong relationships between thermograph measurements and RR, RT and HR in lambs, which are suggested to be directly correlated with heat tolerance capacity of the different genetic groups evaluated in this study. The assessment of body surface temperature measured by the thermograph could be used as a noninvasive tool to assess heat tolerance of the animals.

Comparative hematological analysis of Morada Nova and Santa Inês ewes in all reproductive stages

“…This increase on N/L ratio indicated that ewes in the late pregnancy, postpartum and puerperium were under stress conditions compared to others stages. Some factors can be related to this condition such as fetal growth (late pregnancy), milk production (postpartum), uterine involution (puerperium) and semi-arid conditions (Sejian et al 2014, McManus et al 2015.…”

Infrared thermography as a method for evaluating the heat tolerance in dairy cows

“…In the afternoon, positive correlations were found between BGHI and eye, left-area, and post-udder temperatures. This positive relationship between BGHI and thermographic measurements (except right-area, latudder, and foot) is probably due to increased heat loss in the skin by physiological adaptive mechanisms, avoiding hyperthermia (McManus et al, 2015); in response to heat stress, vasodilation uses the heat dissipation method to attract more heat to the skin surface, increasing blood flow to the periphery (Choshniak et al, 1982). Different temperature points were evaluated using the thermograph in lambs of different genetic groups and it was verified that BGHI was a good indicator of the climatic conditions that affect animals' response (Paim et al, 2012).…”

“…This showed that these measures varied simultaneously in the same direction; increasing physiological parameters corresponds to increase of the temperature of areas photographed with infrared thermography. Due to the greater stress to which the animals were subjected, there was an increase in the physiological parameters as the animals were maintaining the homeothermia and, as a consequence, the thermographic temperatures increased (McManus et al, 2015).…”

Relación de temperatura rectal y frecuencia respiratoria con temperaturas de pelo obtenidas por termografía en ovejas gestantes estresadas por calor

“…En cambio, el monitoreo de la FR es una forma no invasiva para detectar la presencia de estrés por calor en cualquier animal doméstico (Silanikove, 2000); no obstante, contabilizar la FR en ovinos estresados por calor se dificulta en comparación a los bovinos, ya que las respiraciones por minuto (rpm) puede ser superior a 200 (Silanikove, 2000;Marai et al, 2007). Así, lograr establecer un ritmo adecuado para el conteo visual de la FR es difícil, recomendándose repetir el proceso en 2 o 3 ocasiones para disminuir la variación en la medida de dicha variable (McManus et al, 2015). En este sentido, ambas constantes fisiológicas presentan desventajas en su medición, por lo que se requiere la búsqueda de nuevas alternativas para estimar la TR y la FR.…”