|Cheng, Heng Wei|
Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2007
Publication Date: 1/30/2008
Citation: Cheng, H. and Jefferson, L.D. 2008. Different Behavioral and Physiological Response in two Genetic Lines of Laying Hens Following Transportation. Poultry Science. 87:885-892. Interpretive Summary: In the egg production industry, chickens are transferred at least three times during their lifespan, including from grower house to layer house at about 17-wk-old. This practice subjects chickens to stress, resulting from an accumulation of stressors during the process, including capturing, loading and unloading, overcrowding, dehydration, change of temperatures, vibration, novel environments, and fighting for a dominant position following relocation and mixing. These stressors may lead to a deviation from physiological homeostasis, in turn, impairing bird well-being. One solution to these problems is to improve the animal’s ability to cope with the production practices through genetic adaptation. To examine genetic basis of variations in chickens’ physiological and behavioral response to transportation stress, two chicken lines, HGPS and DXL, were used in the study. The HGPS line was selected for high group productivity and survivability resulting from reduced cannibalism and flightiness in colony cages. In contrast, DXL line (Dekalb XL commercial strain) was selected based on individual productivity and is known to have high mortality rates, resulting from aggression and cannibalism, in group housing situations. The data indicate that there are genetic basis of variations in chickens in response to transportation, i.e., the HGPS birds have a better coping capability to transportation stress than the DXL birds. The results further evidence that selective breeding of chickens for genetic or phenotypic features associated with specific behavioral and physiological characteristics is a useful tool to combat problems faced during poultry managements. The data can be adopted by producers and other scientists in designing and conducting research, with an emphasis on improving animal well-being.
Technical Abstract: Physiological and behavioral response to transportation stress were examined in chickens 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 wks of age, 96 pullets per line were randomly assigned to 4-bird cages within the same line. At 17 wks of age, half of the cages of each line (n=12) were randomly used as the experimental group. The birds of the experimental group were transported for 2 h on a country road, and then re-caged in groups of four from the same line, with a caution to ensure all the birds in the same cage were unfamiliar to each other. Behavioral data were collected immediately following the re-caging of the birds. Physical parameters (body and organ weight), plasma corticosterone (CORT) levels, blood and brain serotonin (5-HT) concentrations, and 5-HT1A receptor mRNA expressions were measured at 1 d post-transportation. Results showed that, compared to each strain’s control birds, 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, following transport stress, the HGPS birds had heavier adrenal glands (P<0.01) with higher concentrations of plasma CORT (P<0.01), and a trend to higher central 5-HT levels (P=0.09) with a down-regulated 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 genetic basis of variations in chickens in response to transportation. HGPS birds may have a better coping capability to transportation stress than DXL birds.