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. 2017 Apr;30(4):593-601.
doi: 10.5713/ajas.16.0191. Epub 2016 Jun 6.

Heat tolerance in Brazilian hair sheep

Luiza Seixas  1 , Cristiano Barros de Melo  1 , Candice Bergmann Tanure  1 , Vanessa Peripolli  1 , Concepta McManus  1
Affiliations

Heat tolerance in Brazilian hair sheep

Luiza Seixas et al. Asian-Australas J Anim Sci. 2017 Apr.

Abstract

Objective: The aim of this study was to evaluate heat tolerance using heat tolerance indices, physiological, physical, thermographic, and hematological parameters in Santa Ines and Morada Nova sheep breeds in the Federal District, Brazil.

Methods: Twenty-six adult hair sheep, one and a half years old, from two genetic groups (Santa Ines: 12 males and 4 females; Morada Nova: 7 males and 3 females) were used and data (rectal temperature, respiratory rate, heart rate, skin temperatures; hematological parameters) were collected during three consecutive days, twice a day (morning and afternoon), with a total of six repetitions. Also physical parameters (biometric measurements, skin and hair traits) and heat tolerance indices (temperature-humidity index, Iberia and Benezra) were evaluated. The analyses included analyses of variance, correlation, and principal components with a significance level of 5%.

Results: The environmental indices, in general, indicate a situation of thermal discomfort for the animals during the afternoon. Breed significantly influenced (p<0.001) physiological and physical characteristics of skin, hair, biometric measurements and Iberia and Benezra heat tolerance indices. Santa Ines animals were bigger and had longer, greater number and darker hair, thicker skin, greater respiratory rate and Benezra index and lower Iberia index compared with Morada Nova breed.

Conclusion: Although both breeds can be considered adapted to the environmental conditions of the region, Morada Nova breed is most suitable for farming in the Midwest region. The positive correlation found between the thermographic temperatures and physiological parameters indicates that this technique can be used to evaluate thermal comfort. Also, it has the advantage that animals do not have to be handled, which favors animal welfare.

Keywords: Adaptability; Ewe; Infrared Thermography; Physiology; Thermal Stress.

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Figures

Figure 1
Figure 1
First two autovectors for heat tolerance indices and physiological and physical traits in sheep in the Federal District, Brazil. RT, rectal temperature (°C); HR, heart rate (beats/min); RR, respiratory rate (movements/min); SH, shoulder height; TP, thoracic perimeter; BKL, back length; BL, body length; RuH, rump height; RW, rump width; BW, breast width; ST, skin thickness; HT, hair thickness; NH, number of hairs; HL, length of hair; L*, brightness; chromatic channels representing b*, yellow-blue; a*, red-green (CIELAB).
Figure 2
Figure 2
First two autovectors for heat tolerance indices, thermograph temperatures and physiological and physical traits in sheep in the Federal District, Brazil. RT, rectal temperature (°C); HR, heart rate (beats/min); RR, respiratory rate (movements/minute); ST, skin thickness; HT, hair thickness; NH, number of hairs; HL, length of hair; L*, brightness; chromatic channels representing b*, yellow-blue; a*, red-green (CIELAB).
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