There are potential advantages for using noninvasive methods instead of conventional approaches for measuring corticosterone (CORT) as a metric of stress. Two studies compared blood heterophil: 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 sampling 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 treatment after 24 h, whereas in study 2 colon content CORT concentrations were elevated after 6 h. CORT treatment increased body and primary feather CORT and primary feather CORT increased with time in control groups in both studies. Serum CORT exhibited the lowest variability compared with all other sample sources used for determining CORT. Estimates of CORT by different methods were positively correlated. These results 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.

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Stress and leg weakness are detrimental to broiler production, health, and welfare. Traditional methods to evaluate stress may be stressful to the bird because they are invasive and require handling and restraint. Two studies examined the effects of light intensity and flooring on the following in broilers: 1) traditional methods for assessing stress using heterophil-to-lymphocyte ratios and serum corticosterone ( CORT ) concentrations, 2) noninvasive measures of stress from infrared thermography ( IRT ) eye and beak surface temperatures, and 3) latency-to-lie ( LTL ) test times of birds tested individually and in groups of 5. Day-of-hatch male broiler chicks were placed into 6 pens (N = 120 chicks/pen). At 1 wk, pens were allocated to 3 light intensity treatments (2, 5, or 10 lux). At 4 wk, half of the birds from each pen were moved to a pen with wire flooring and the same light intensity. At 1, 4, 5, and 8 wk, blood samples were collected and IRT images of the heads of 5 clinically healthy broilers from each pen were captured. In study 2, IRT images of the heads of birds that became lame in the wire flooring pens were taken. There were no treatment effects on the LTL times of birds tested in groups or individually ( P > 0.05). On day 56 in study 1, birds on wire flooring had elevated heterophil-to-lymphocyte ratios and CORT concentrations ( P ≤ 0.002) and depressed IRT eye and beak temperatures ( P < 0.0001). In both studies, there were negative correlations between CORT concentrations and IRT beak surface temperatures ( P < 0.05). Lame birds had lower IRT eye and beak surface temperatures than sound birds ( P ≤ 0.004), and the IRT beak surface temperatures of lame birds were lower than their eye surface temperatures ( P = 0.004) in study 2. These studies indicate that the IRT surface temperatures of the eye, and more distinctly of the beak, can be used as sensitive noninvasive indicators of stress.

Consumer concern for broiler welfare has increased interest in chicken from slower growing ( SG ) broiler strains. Broilers from SG strains take longer to reach market weight, which may necessitate differences in management practices, such as stocking density. This study evaluated the effects of 2 stocking densities on production performance, body conformation, and welfare of broilers from 2 strains. Broilers from strains that reach market weight at age 42 D (CONV; N = 284) and at 63 D (SG; N = 284) were exclusively stocked into pens at a density of either 29 kg/m 2 or 37 kg/m 2 . Birds were provided the same starter, grower, and finisher diets with diet phase changes occurring when SG bird body weight ( BW ) matched CONV. Live BW, body length, pelvic width, shank length, shank width, keel length, breast width, and breast depth were collected at 4 phases: Phase 1—chick placement, Phase 2—starter, Phase 3—grower, and Phase 4—finisher. At Phase 4, footpad dermatitis ( FPD ), hock burn ( HB ), and toe damage ( TD ) were scored. Feed conversion ratio ( FCR ) and mortality for each pen were recorded throughout the study. Final BW was similar (2.68 kg) for both strains and stocking densities of birds ( P > 0.05). CONV bird FCR was 35% more efficient than SG ( P < 0.0001). CONV birds had shorter bodies and shanks compared with SG birds at Phases 3 and 4 ( P < 0.05). Slower growing birds stocked at 37 kg/m 2 had the longest bodies and keel bones at Phase 4 ( P < 0.01). Also at Phase 4, SG birds stocked at 29 kg/m 2 had the lowest prevalence of HB (4%), yet the highest prevalence of TD (28%; P < 0.01). These results indicate differences in the effects of strain and stocking density on male broiler conformation, performance, and welfare and highlight the importance of tailoring management practices to the strain of broiler raised.

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