| dc.description.abstract | The environment and incubation circumstances in which a chicken embryo develops are crucial to a chicken’s life, as those circumstances can affect the chickens’ welfare throughout its life and their ability to cope with stressors. Light during incubation may cause reduction in fear responses and a decrease in stress indicators. The level of corticosterone in the feathers represents an integrated measurement of the hypothalamic-pituitary-adrenal activity over a long period of time. This present research investigated the level of corticosterone in flight feathers and the latency to leave the start box during an emergence test to evaluate the effect of a light-dark cycle during incubation on two genetic lines of layer hens, the ISA Brown and the Dekalb White Leghorn. More specifically, the effect of the light incubation on the chickens’ behavior, fear responses, stress and welfare was investigated. In total 20 chickens were euthanized and four feathers per chicken were plucked. Flight feathers number 2 and 8 from the left and right wing were used. These feathers were visually observed on irregularities and weighed, and the length was measured. Corticosterone concentrations were measured in the feather vanes using an ELISA. In addition, an emergence test was performed on 38 chickens in order to assess fear and investigate the chickens’ adaptation to new environments. No significant difference was found in corticosterone concentrations between incubation treatments or genetics for different feathers. Fungi were found in a total of 40 feathers, which appeared to lower the corticosterone concentrations. The Dekalb white chickens had significant longer and heavier feathers compared to the ISA Brown chickens. During the first day of the emergence test, the Dekalb white chickens and the light treatment groups took longer to leave the start box. On the other test days no difference was found between genetics or incubation treatments. The time to leave the start box decreased each day, but it did not depend on treatment of genetics, as the day influenced the genetic differences. Based on this research, it has not been proven that the light during incubation can increase the chickens’ ability to cope with stressors compared to dark incubation. Further research for the corticosterone concentrations will have to be carried out with a larger sample size, with the feathers packed in the right way to prevent fungus, in order to make valid conclusions. Further research also needs to be carried out to conclude if the chickens are faster to leave the start box due to less stress, increased social motivation or because they habituated to the test. | |
