Time Course Changes in the Blood Parameters and the Expression of Diencephalic CRH and AVT mRNA Due to Acute Isolation Stress in Chicks

Abstract

It is important to quantify and estimate stressful stimulation because stress appears to limit productivity and welfare in poultry. The purpose of this study is to investigate the effect of acute isolation stress (5, 10 or 30min) on the levels of blood parameters (glucose, free fatty acid (FFA) and corticosterone (CORT)) and diencephalic stress related peptide gene expressions (corticotrophin-releasing hormone (CRH) and arginine vasotocin (AVT)) in neonatal chicks. Although the isolation treatment did not affect concentration of plasma glucose (P>0.05), plasma FFA at 30min after treatment was higher than control (P<0.01). The level of CORT increased significantly after 5 and 10min of treatment (P<0.01), but that significant increase had disappeared in the chicks isolated for 30min. The expression level of CRH in the chicks treated for 10min, but not in the chicks treated for 5 and 30min, was higher than in control (P<0.01), whereas there was no change in AVT mRNA for any of the isolation treatments (P>0.05). These findings demonstrate that high levels of CORT, through negative feedback, decrease CRH synthesis until 30min after isolation, and further suggest that AVT expression in the diencephalons may not be applicable as an indicator of acute isolation stress in neonatal chicks.