ANIMAL WELL-BEING AND BEHAVIOR An evaluation of methods for measuring stress in broiler chickens Shawna L. Weimer, *, 1 Robert F. Wideman, * Colin G. Scanes, * Andy Mauromoustakos, † Karen D. Christensen, * and Yvonne Vizzier-Thaxton * * Department of Poultry Science, University of Arkansas, Fayetteville, AR, 72701, USA; and † Agricultural Statistics Lab, University of Arkansas, Fayetteville, AR, 72701, USA ABSTRACT There are potential advantages for us- ing noninvasive methods instead of conventional ap- proaches for measuring corticosterone (CORT) as a metric of stress. Two studies compared blood het- erophil: lymphocyte (H:L) ratios, serum CORT, cecal content CORT (Study 1), colon content CORT (Study 2), and feather CORT concentrations for broiler chicks receiving drinking water with or without added CORT. On day 28, male broilers (N = 140) were provided tap water (Control group) or water containing 20 mg/L of CORT (CORT group) for up to 72 h. Body weight (BW), blood, feather, cecal, and colon content samples were collected from 10 birds from each treatment group at 0, 6, 12, 24, 30, 48, and 72 h. Data were analyzed with a JMP Pro ANOVA. Mean comparisons were analyzed on significant treatment effects using post hoc t-tests to compare control and CORT measures within each sam- pling time point. Pearson’s pairwise correlations for all data were performed. A treatment by time interaction affected all measures in both studies. In both studies, CORT treatment reduced body weight and increased H:L ratios at later time points. In study 1 cecal content CORT concentrations were elevated with CORT treat- ment after 24 h, whereas in study 2 colon content CORT concentrations were elevated after 6 h. CORT treat- ment increased body and primary feather CORT and primary feather CORT increased with time in control groups in both studies. Serum CORT exhibited the low- est variability compared with all other sample sources used for determining CORT. Estimates of CORT by different methods were positively correlated. These re- sults indicate that serum CORT concentrations most reliably reflect the CORT status of broilers, and that feather CORT concentrations demonstrated potential for estimating stress in broilers. Key words: broiler, corticosterone, feather, stress, well-being 2018 Poultry Science 97:3381–3389 http://dx.doi.org/10.3382/ps/pey204 INTRODUCTION Stress has a detrimental impact on broiler per- formance (Virden and Kidd, 2009; Vizzier-Thaxton et al., 2016). Stressors activate the hypothalamo- pituitary-adrenocortical cascade, resulting in the release of corticosterone (CORT) (Blas, 2015). The concentration of CORT in serum or plasma provides an indication of an individual bird’s acute stress status at the time the blood was drawn (Bortolotti et al., 2008; Blas, 2015), which can be confounded by fear of humans (Hemsworth et al., 1994) and the stress of capture, handling, and restraint (Kannan and Mench, 1996; Bortolotti et al., 2008; Alm et al., 2014). Drawing blood longer than 2 min after bird capture yields blood samples with higher CORT concentrations (Morm` ede et al., 2007; Chloupek et al., 2011). Serum or plasma C  2018 Poultry Science Association Inc. Received January 10, 2018. Accepted June 6, 2018. 1 Corresponding author: slweimer@purdue.edu CORT concentrations often are measured in combi- nation with heterophil to lymphocyte (H:L) ratios, as increases in H:L ratios reflect the response of the im- mune system to chronic stress associated with sustained elevations in circulating CORT concentrations (Gross and Siegel, 1983; Shini et al., 2008; Scanes, 2016). Noninvasive measures of CORT potentially can offer more convenient and less disruptive alternatives to traditional measures that require restraint and blood sampling. Validating objective, repeatable noninvasive measures of CORT would greatly improve our ability to rapidly assess the impact of various animal stressors on broiler performance (Post et al., 2003; Bortolotti et al., 2008; Fairhurst et al., 2013). Noninvasive measures include measurements of CORT concentrations in the excreta (Dehnhard et al., 2003; Alm et al., 2014) and feathers (Bortolotti et al., 2008; Lattin et al., 2011; Fairhurst et al., 2013; Carbajal et al., 2014). The concentrations of CORT deposited in the excreta, per se or an average of CORT accumulation following metabolism and during the process of excretion, have previously been measured as an indicator of stress in 3381 Downloaded from https://academic.oup.com/ps/article-abstract/97/10/3381/5036946 by guest on 25 March 2019