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J Dairy Sci. 2014 Dec;97(12):7685-90. doi: 10.3168/jds.2014-8444. Epub 2014 Oct 3.

Short communication: Factors affecting hair cortisol concentrations in lactating dairy cows.

Author information

1
Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC, V6T 1Z4 Canada.
2
Agriculture & Agri-Food Canada, Agassiz, BC, V0M 1A0 Canada.
3
Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran 91775-1163.
4
Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC, V6T 1Z4 Canada. Electronic address: ronaldo.cerri@ubc.ca.

Abstract

Cortisol has long been used as a marker of the stress response in animals. Cortisol can be analyzed from different media, most notably from the blood, saliva, and feces; however, the collection of cortisol from some of these media requires invasive procedures or excessive handling of the animals. Furthermore, it is not possible to capture long-term increases in circulating concentrations of cortisol from the blood, saliva, or feces. Hair cortisol has been found to be a reliable alternative for measuring chronic stress. With this emerging measure, appropriate sampling methodology must be developed and validated. The aim of this study was to determine the effects of hair color, sampling location, and processing method on cortisol concentrations in hair from lactating black and white Holstein cows (n=18). Furthermore, we aimed to measure the hair growth rates at different body locations (n=12) and test hair cortisol levels when resampled over short intervals (n=37). Both black- and white-colored hair was collected from the shoulder, top line, hip, and tail switch of Holsteins; due to breed characteristics only white hair was harvested from the tail switch. All samples were cleaned with water and isopropanol, and then ground in a ball mill or finely cut with scissors once dry. Cortisol was extracted with methanol before being measured using a commercially available ELISA kit. Concentrations of cortisol were greater in white than in black hair (7.8 ± 1.1 vs. 3.8 ± 1.1 pg/mg). When only white samples were analyzed, hair from the tail switch had more cortisol than hair from the shoulder (11.0 ± 1.2 vs. 6.2 ± 1.2 pg/mg), whereas no difference was found when compared with the hip and top line. Samples ground with a ball mill had greater concentrations of cortisol extracted than those minced with scissors (10.4 ± 1.2 vs. 4.7 ± 1.2 pg/mg). The growth rate of hair was significantly greater at the tail switch compared with the hip and shoulder (0.51 ± 0.05 vs. 0.04 ± 0.05 vs. 0.03 ± 0.05 mm/d). When hair was collected every 3 wk after calving, a tendency was detected for multiparous cows to have greater concentrations of hair cortisol and significantly greater concentrations of cortisol on d 0 and 21 after calving compared with d 42, 84, and 126. In Holsteins, the hair on the tail switch is always white, grows more rapidly than other sites, and is sensitive enough to capture changes in cortisol over intervals as short as 3 wk, making it the ideal location for measuring hair cortisol.

KEYWORDS:

Holstein cow; hair cortisol; stress

PMID:
25282411
DOI:
10.3168/jds.2014-8444
[Indexed for MEDLINE]
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