Comparison of Stress Response between Korean Native Chickens and Single Comb White Leghorns subjected to a High Stocking Density

Department of Animal Science and Biotechnology, Gyeongnam National University of Science and Technology, Jinju 660-758, KoreaABSTRACT With Single Comb White Leghorn (WL) and Korean Native Chicken (KNC) breeds, we compared the stress response with chicken breeds that were subjected to a high stocking density. Stress response was analyzed by the quantity of telomeric DNA, the rate of DNA damage and the expression levels of heat shock proteins (HSPs) and hydroxyl-3- methyl-glutaryl coenzyme A reductase (HMGCR) genes on tissues and blood. The telomere length and telomere shortening rates were analyzed by quantitative fluorescence in situ hybridization on the nuclei of lymphocytes and tissues. The DNA damage rate of lymphocytes was quantified by the comet assay. The expression levels of HSP70, HSP90-α, HSP90-β and HMGCR genes were measured by quantitative real-time polymerase chain reaction in lymphocytes. There was no significant difference between KNC and WL in body weight, weight gain, telomere shortening rate and DNA damage rate. However, the growth rate significantly decreased in chickens raised under high stocking density conditions, as compared to the control group. The telomere-shortening rate, DNA damage and HSPs expression of the lymphocytes were significantly higher in the high stocking density group than the control. The stress condition and breeds had a significant effect on the expressions of HSP70, HSP90-α and HSP90-β in lymphocytes, except HMGCR. The stress response of WL was higher than that of KNC, as analyzed to the expression of HSP70 and HSP90-α. Therefore, we concluded that the chickens which were exposed to a high stocking density had increased the individual physiological stress response regardless of breeds, and White Leghorns are more susceptible to stress condition than Korean Native Chickens.(Key words : stress response, telomere, DNA damage, HSP, Korean Native Chicken, Leghorn)