Identification of genes related to heat stress in Santa Inês sheep

Abstract

The current climate change scenario has accentuated the frequency of heat waves and raised the average temperature in different regions of the world, increasingly exposing animals to stressful environmental situations. Thus, it is important to study the animals' adaptation to extreme weather events or faster climate changes and how the animal is able to respond to these events and what will be the impact on its thermolytic performance. The general objective of the study is the identification of genes in the skin related to thermal stress, after characterizing heat tolerance by physiological, metabolic, and behavioral changes, using the Santa Inês breed as a model. The experiment will be conducted at the Fernando Costa Campus (FZEA) of the University of São Paulo, Brazil. Eighty Santa Inês sheep (black coat) will be used, randomly distributed in 4 experimental groups (20 animals), each group will be kept 7 days in the climatic chamber with an average temperature of 36°C (10 am to 4 pm) and with maintenance of 24°C from 4 pm to 10 am. The intravaginal temperature will be measured continuously during each cycle and at the end of each cycle (days 7 and 8) sampling of rectal temperature and respiratory frequency, loss of transepidermal water, temperature of the ocular surface and temperature of the left antimere by infrared thermography, temperature tympanic and blood for T3 concentration analysis at 1 pm, 4 pm, 7 pm, 9 pm, 1 am, 4 am, 7 am, 10 am. Also, skin samples will be taken for histological examination, in order to assess the structure and morphology of the sweat glands in the basal period (spring) and after prolonged stress (day 8). All variables collected will be used to select the 12 most heat tolerant animals and the 12 least heat tolerant animals, and only in these will gene expression in skin samples be evaluated. For data analysis, evaluation times, phenotype (more tolerant or less tolerant to heat) and their interactions and the animal as a repeated measure over time will be considered as a fixed effect. Multiple comparisons will be performed by Tukey at 5% probability. (AU)