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Two experiments were conducted to determine whether previously handled male broilers would show a decreased corticosterone (CORT) response to commercial-type handling at market age. In Experiment 1, broilers (N = 36) were either repeatedly handled (H) or non-handled (NH) from day 1 to 6 weeks of age. At 7 weeks, they were exposed to either a three-bird inverted (multiple inverted, MI), one-bird inverted (single inverted, SI) or upright (U) handling treatment for 2 min. Plasma CORT levels were determined at 1 h or 3 h after the handling treatments were imposed. Although CORT levels were higher (average 2 ng ml-1) in the NH than in the H pre-treatment group in response to handling, this difference was not significant except for H birds handled in the SI position, resulting in a significant interaction effect (P < 0.05). CORT levels were lower in both groups after U as opposed to MI or SI handling (P < 0.03). In Experiment 2, broilers (N = 216) were subjected to one of three pre-treatments--repeated upright handling (RU), repeated inverted handling (RI), or no handling (NH)--every day until 6 weeks of age. At 7 weeks of age birds in each pre-treatment group were then exposed to either the MI, SI or U handling treatment for 2 min. Blood samples were collected at 0, 1, 3 and 4 h after handling. Again, U handling resulted in a lower (P < 0.001) CORT response than MI or SI handling across pre-treatments. CORT levels were higher (P < 0.001) at 0 h than at the other time periods. Pre-treatment had no significant effect on CORT levels, and there was no interaction among any of the factors. These results show that upright handling is less stressful to broilers than inverted handling, and that stress levels are highest immediately after handling. However, there is little evidence that the CORT response to handling at market age can be markedly or reliably reduced by prior handling during rearing.
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