Effects of Intracerebroventricularly Administered Carbetocin on Social Behavior in Holstein Steers

Abstract

To shed light on the role of central oxytocin (OXT) in regulating social behavior in cattle, the impact of intracerebroventricularly administered OXT agonist, carbetocin (CBT), on the social behavior of a group of familiar steers was investigated. In the first experiment, we determined the dose response of intracerebroventricularly administered CBT (0.5, 5 or 50 nmol) on plasma cortisol level and behavior using 7 steers aged from 6 to 10 months. Five of the steers were assigned to the second experiment. CBT (50 or 200 nmol/200 μl) in artificial cerebrospinal fluid (aCSF) or aCSF (200 μl) was injected into the third ventricle. Immediately after the injection, the animal and two peers were taken outside to the adjacent paddock. Thirty minutes later, maintenance and social behaviors of the animal were observed for 2 hr. CBT had no effect either on the basal cortisol level or on the maintenance and the abnormal behavior in steers with their movement restricted by a stanchion stall in the first experiment. However, in the same steers with no movement restrictions in the second experiment, CBT facilitated lying, probably because of its sedative effect via OXT receptor activation, which disturbed some aspects of social behavior. These results suggest that central OXT receptor activation might not affect social behavior itself among "familiar members", because the stimulation of the central OXT system by intracerebroventricular administration of CBT did not facilitate social behavior between familiar steers.