Differentiation of stress load resistant calves by the help of insulin-like growth factor–I (IGF–I) in serum

Abstract

Animals do not respond uniformly to stress load. It leads to energy losses and body damage during stressor exposure. One of the hormones activated by stress, providing the repair of the body during and after load, is growth hormone. It acts directly on cells, but mainly through insulin-like growth factor-I (IGF-I), which protects cells from apoptosis and promotes their growth and proliferation. Changes in concentrations of IGF-I in the circulation during psychical load at individual excitatory types of calves (EHb+ highly reactive, EHb° medium reactive and EHb- low reactive) are not known. Calves type EHb+ and EHb° are more resistant to stress than EHbtype calves. The aim of our study was to measure the levels of IGF-I immediately after the application of psychical form of load with the calves differentiated according to different types of excitation. Differentiation of excitatory types of calves was done after 20 minute habituation test. Habituation test was performed in habituation chamber. Immediately before and after habituation calves were taken blood from jugular vein by syringe. Blood sampling was allowed to clot in a refrigerator at 4 °C and after 4 to 6 hours, it was centrifuged at 1200 rpm for 10 min. Then serum was drawn in from the syringe and frozen in aliquots volume in eppendorf vessel until further processing at -20 °C. Serum samples of calves were treated enzyme-linked immunosorbent assay ELISA - test. The highest levels of IGF-I in all types of calves were in the resting blood collection. Within of individual type of excitation in a concentration IGF-I before and after load significant difference was not found. After application of psychical form of stress the concentration of IGF-I in blood of the calves declined.