ADRENOCORTICAL RESPONSE OF CALVES TO TRANSPORT STRESS AS MEASURED BY SALIVARY CORTISOL

Abstract

A new approach utilizing a "nonstressful" technique of saliva collection and determination of salivary cortisol by radioimmunoassay was used to monitor the adrenocortical response of calves to repeated transport stress. Four standardized trucking and sampling procedures were used with 19 calves previously trained to being mustered into a race (chute) and having saliva collected. Basal mean salivary xortisol levels in the 19 calves ranged from 0.3 ± 0.4 nmol L−1 to 3.4 ± 0.6 nmol L−1, and after 30 min of trucking manoeuvres (starting, turning, reversing and stopping), significant increases (P < 0.01) in mean salivary cortisol levels occurred on all four occasions to values ranging from 10.5 ± 1.4 nmol L−1 to 16.0 ± 2.3 nmol L−1. After a further 2 h of normal road transport mean levels of salivary cortisol were still significantly elevated (P < 0.05) and ranged from 4.0 ± 0.9 nmol L−1 to 11.3 ± 2.6 nmol L−1 in comparison with 0.5 ± 0.2 nmol L−1 to 1.4 ± 0.3 nmol L−1 for nine control calves (not transported). Salivary cortisol levels returned to pretreatment levels within 2 h post-transport. There was a tendency for Friesian calves, less than 1 mo of age, to have a lower adrenocortical response to transport than crossbred calves of the same age. No evidence was found for adaptation of the adrenocortical response of the calves to transport. Key words: Adrenocortical response, calves, transport stress, salivary cortisol