Wool cortisol is a better indicator of stress than blood cortisol in ewes exposed to heat stress and water restriction

Abstract

This study investigated the effect of water restriction on wool and blood cortisol concentrations and water consumption patterns in heat-stressed sheep. Nine Corriedale female sheep (average BW = 43 ± 6.5 kg) were individually fed diets based on maintenance requirement in metabolic crates. They were assigned to three treatments according to a Latin square design (3 × 3) for three periods with a 21-day duration for each period (nine sheep per treatment). Treatments included free access to water (FAW), 2 h water restriction (2hWR) and 3 h water restriction (3hWR) after feeding. Average temperaturehumidity index in the experimental room was 27.9 throughout the experiment that defines heat stress conditions. Wool samples were taken at the end of each period on day 21. No differences were found in cortisol concentration in each fragment (dried, washed and residual extract) of wool (P < 0.05). Total wool cortisol concentration was higher in the 3hWR group than the other treatments (P < 0.05). Blood cortisol was not different among the treatments (P > 0.05) and resulted in higher variable data compared with wool cortisol. Blood neutrophils and neutrophil/lymphocyte ratio suppressed in FAW and 3hWR groups compared with the 2hWR group (P < 0.05). The duration of water consumption recorded after feeding in the 3hWR group was higher than in the 2hWR group when recorded in the afternoon (P < 0.01). Water consumption rate was higher in the 3hWR group than in the 2hWR group (P < 0.01). However, total water consumed was lower in the 3hWR group compared with other treatments (P > 0.05). It can be concluded that wool cortisol provides more precise and accurate data than blood cortisol during heat stress conditions. Water restriction for 3 h after feeding can act as a stressor and is critical for sheep during heat stress as the consumption of water decreases with restriction.

Assessment of chronic stress in sheep (part I): The use of cortisol and cortisone in hair as non-invasive biological markers

“…In recent years, the use of hair cortisol as a biomarker of chronic stress has attracted much attention (Acorsi et al, 2008;Gow et al, 2010;Russel et al, 2012;Ghassemi et al, 2014).…”

Coat and hair color: hair cortisol and serotonin levels in lactating Holstein cows under heat stress conditions

“…HC concentration may provide precise and reliable data because the level changes with a positive correlation to stressors (Kalra et al ; Yamada et al ). Moreover, HC in cattle could help the farmers to monitor the stress levels and well‐being of their animals, and more closely evaluate individual resilience to stressors (Comin et al 2012a; Ghassemi Nejad et al 2014b; Charney ).…”

“…Preparing hair for cortisol analysis included shaving the hair from the forehead, wrapping the hair in aluminum foil, unwrapping and washing with isopropanol and methanol, drying, grinding and then applying HC assay using a kit according to manufacturer's recommendation (Salimetrics, high sensitivity salivary cortisol, enzyme immuneassay kit, no. 1‐3002, State College, PA, USA, 16803) described in details by Ghassemi Nejad et al (2014b). Blood for serum collection was taken from the jugular vein of each cow into a 10 mL sterile tube for 3 consecutive days at the end of the experiment.…”

A Cortisol Study; Facial Hair and Nails

“…Measuring cortisol levels in saliva, blood and urine for short term HPA activity can be problematic due to fluctuations in cortisol levels [6,14,15]. Collecting blood is invasive and may be anxiogenic, while urine collection takes a twenty-four hour period.…”

“…Saliva sampling is also problematic due to the influence of food ingredients or medications which may contaminate results. Cortisol extraction from hair (facial hair in particular) and nails (finger and toe) may eliminate these issues and can be validated as a reliable means of assessment [6,8,15].…”