Physiological responses of Rasa Aragonesa ewes to water restriction

Global climate change impacts livestock production, particularly in extensive or semi-extensive systems in semi-arid regions, due to the temperature increases and water scarcity. The aim of this study was to characterize the different physiological responses of Rasa Aragonesa ewes to water restriction. Two hundred and two ewes were challenged to total water restriction for 5 days. Temperature and relative humidity were measured to calculate the temperature-humidity index (THI). According to the THI, ewes were also under heat stress conditions. Daily, dry matter intake (DMI), body weight (BW) and body condition score (BCS) were also recorded. Blood samples were collected on days 0, 1 and 5. Wool samples were collected on days 0 and 28. Blood samples were used for classic hematological and some biochemical parameters (total proteins, glucose, NEFAs, cortisol, dehydroepiandrosterone (DHEA), and its sulphate (DHEA-S)). In the wool cortisol, DHEA and DHEA-S were also measured. Principal component analysis (PCA) and hierarchical clustering (HC) were carried out to classify ewes according to their stress response. DMI, BW and BCS significantly lowered during the water stress period (<italic>p</italic> &lt; 0.05). Most hematological and biochemical parameters were affected (<italic>p</italic> &lt; 0.05), except for blood cortisol and the blood cortisol:DHEA-S ratio (<italic>p</italic> &gt; 0.05). After HC analysis, ewes were classified into three clusters based on their stress tolerance. Cluster 1 (C1, n=168) included the most tolerant ewes, followed by Cluster 2 (C2, n=22) and Cluster 3 (C3, n=12), which was the least tolerant. The C3 ewes had the highest blood cortisol and non-esterified fatty acid mobilization, which were associated with the greatest BW loss. In conclusion, the stress conditions affected hematological and biochemical parameters in blood and wool. The majority of Rasa Aragonesa ewes generally demonstrated good tolerance to these stressors (C1, n=168), with only 34 ewes classified as less tolerant.