Cortisol and corticosterone, hormones traditionally considered biomarkers of stress, can be measured in fluid biomatrices (e.g., blood, saliva) from live animals to evaluate conditions at sampling time, or in solid biomatrices (e.g., hair, feather) from live or dead animals to obtain information regarding long-term changes. Using these biomarkers to evaluate physiological stress responses in domestic animals may be challenging due to the diverse characteristics of biomatrices for potential measurement. Ideally, a single measurement from the biomatrix should be sufficient for evaluating chronic stress. The availability of appropriate and cost-effective immunoassay methods for detecting the biomarkers should also be considered. This review discusses the strengths and limitations of different biomatrices with regard to ensuring the highest possible reliability for chronic stress evaluation. Overall, solid biomatrices require less frequent sampling than other biomatrices, resulting in greater time-and cost-effectiveness, greater ease of use, and fewer errors. The multiplex immunoassay can be used to analyze interactions and correlations between cortisol and other stress biomarkers in the same biomatrix. In light of the lack of information regarding appropriate biomatrices for measuring chronic stress, this review may help investigators set experimental conditions or design biological research.

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Different methodologies in hair cortisol extraction may alter the final output. Thus finding the standard methodology according to a laboratory facilities is pivotal. This study was carried out to validate the feasibility of two methods of grinding hair for cortisol extraction in Korean native (Hanwoo) cattle. Hair from nine cattle including mature cows, heifers, and calves were assigned to one of the following methods for grinding hair; 1) using bead beater (BB) and 2) using surgical scissors (SS). Hair samples (> 1 g) were harvested from forehead of each individual twice (first and second measurement) to validate the results. To improve the accuracy of the obtained data, each sample was duplicated into two wells during enzyme immunoassay (EIA) analysis. Overall comparison of hair cortisol concentration (HCC) showed that the data within the range (out of the range) of standards provided by the EIA kit were 88.9% (11.1%) and 66.7% (33.3%) for BB compared with SS, respectively. In the first measurement, application of BB was tended to show higher ( p = 0.056) amount of HCC compared with SS. In the second measurement application of BB showed higher ( p = 0.0028) amount of HCC compared with SS. Among the cattle, calves showed higher HCC using BB compared with SS ( p < 0.05). Application of BB in hair grinding methodology for Hanwoo cattle may improve cortisol extraction in comparison to application of SS method, with more consistency. Thus, it would be the preferable method to use.

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