Study on environmental indices and heat tolerance tests in hair sheep

Abstract

The ability to predict the effects of climatic factors on animals and their adaptability is important for livestock production. The aim of the present study was to analyze whether existing indices are suitable for evaluating heat stress in Santa Ines and Morada Nova sheep, which are locally adapted hair sheep breeds from northeastern Brazil, and if the limits used to classify thermal stress are suitable for these breeds. Therefore, climatic, physiological, and physical parameters, as well as thermographic images, were collected in 26 sheep, 1 1/2 years old, from two genetic groups (Santa Ines 12 males and 4 females; Morada Nov. 7 males and 3 females) for 3 days in both morning (4:00 a.m.) and afternoon (2:00 p.m.) with six repetitions, totalizing 156 repetitions. Statistical analysis included correlations and broken-line regressions. Iberia and Benezra indices were the tolerance tests that best correlated with the assessed parameters. High correlations between environmental indices and rectal or skin surface temperatures was observed, which indicates that these indices can be used for Santa Ines and Morada Nova sheep raised in central Brazil. However, some indicative values of thermal discomfort are different from the existing classification. Therefore, in order to classify appropriately, the model used needs to be carefully studied, because these classifying values can vary according to the species and model. Further research is necessary to establish indicators of thermal stress for sheep breeds raised in the region.

Variaciones en las respuestas termoregulatorias de ovejas de pelo durante los meses de verano en un clima desértico

“…Cabe mencionar que la T en las mañanas fue <30 ºC en todos los meses, situación que pudo favorecer el alivio temporal diario de las ovejas en las condiciones de hipertermia (15) . El tipo de estrés calórico que prevaleció durante el estudio varió de moderado (junio, julio y septiembre) a severo (agosto) (16,17) . En las tardes de agosto, el estrés calórico llegó a ser de tipo emergente (≥ 84 unidades).…”

“…En el presente estudio, se detectaron variaciones en la TR, FR y temperaturas de capa de pelo en todos los meses de verano, de acuerdo con los cambios en la T y el ITH observados a través del día. Estos hallazgos coinciden con otras investigaciones donde las variables fisiológicas aumentaron con el incremento en la T a través del día, tanto bajo condiciones de estrés calórico como de termoneutralidad (10,15,17) .…”

Placental Development and Physiological Changes in Pregnant Ewes in Silvopastoral and Open Pasture Systems during the Summer

“…The surface temperature can be used as a parameter for evaluating the thermal comfort of sheep, as there is a correlation between environmental indices and rectal and skin surface temperature [33]. Thus, the highest value of MST was detected for the OP system, where the highest temperatures were observed.…”

Research Article Genealogical and genomic heritability for adaptability and reproductive traits in the Colombian Creole cattle breeds Blanco Orejinegro and Sanmartinero

“…The Iberian heat tolerance test or heat tolerance coefficient (HTC) proposed by Rhoad, (1944) and modified by Bianca (1963), and the Benezra test (1954) or coefficient of adaptability (CA), are indices extensively used to measure the degree of heat tolerance in cattle and other species living under stressful environmental conditions (Da Rocha et al, 2012;Da Silva et al, 2015;Seixas et al, 2017).…”