Different behavioral and physiological responses in two genetic lines of laying hens after transportation.

Physiological and behavioral responses to transportation stress were examined in a chicken strain selected for high group productivity and survivability (HGPS) resulting from reduced cannibalism and flightiness in colony cages and in chickens from Dekalb XL (DXL) commercial strain. At 13 wk of age, 96 pullets per strain were randomly assigned to 4-bird cages within the same strain. At 17 wk of age, half of the cages of each strain (n = 12) were randomly used as experimental group. The birds of the experimental group were crated by line, with a caution to ensure all the birds in the same cage were unfamiliar to each other, and then transported for 2 h on a country road. After transportation, the birds were recaged in groups of 4 within the same line. Behavioral data were collected immediately after the recaging of the birds. Physical parameters (BW and organ weight), plasma corticosterone levels, blood and brain serotonin (5-HT) concentrations, and 5-HT1A receptor mRNA expressions were measured at 1 d posttransportation. Results showed that, compared with the control birds of each strain, transportation stress-induced behavioral changes in eating, drinking, and preening were found in the birds from both strains, but the HGPS birds showed a greater increase in drinking and preening (P < 0.01). In addition, after transportation stress, the HGPS birds had heavier adrenal glands (P < 0.01) with higher concentrations of plasma corticosterone (P < 0.01) and a trend to higher central 5-HT levels (P = 0.09) with a downregulated 5-HT1A receptor gene expression (P < 0.05), whereas the DXL birds had a higher H:L ratio (P < 0.05). The data indicate that there are a genetic basis of variations in chickens in response to transportation stress. The HGPS birds may have a better coping capability to transportation stress than DXL birds.