The Relationship between Individual Behavioural Characteristics and Physiological Responses to Isolation Stress in Holstein Heifer

Abstract

The aim of this study was to identify individual difference in response to social isolation in heifers. Eight Holstein heifers (77 to 88 weeks old) were used. For the social isolation, one test cow and two other peers were maintained in the same room for 3 days, then the test heifer was isolated in its own room by removing the peers for 7 hours. The duration (sec) of specific behavioural categories (standing, rumination with standing, sitting, rumination with sitting, feeding, access to water) and the number of vocalizations during the isolation were scored. These behavioural data were analyzed using a principal component test with the covariance matrix. Blood samples were collected every 30min during isolation through the jugular catheter for the assay of ACTH and cortisol. Heart rate (HR) was continuously recorded by a HR recording system for human exercise. A principal component test extracted two principal factors from the behavioural scores and the first and the second principal component were designated “activity” and “anxiety”, respectively. When the correlation between these two factors and plasma concentrations of ACTH and cortisol, and HR were analized by Spearman’s ranked correlation analysis, the second principal component, anxiety, was correlated with the plasma cortisol concentration (r=-0.76, P<0.05). These results suggest that individual Holstein heifers express different behavioural characteristics during isolation stress and anxious-type heifer tended to have a higher plasma cortisol concentrations during the isolation.