Effect of temperament and prolonged transportation on endocrine and functional variables in young beef bulls.

The purpose of this study was to evaluate the effect of prolonged transportation on adrenocorticotropic hormone (ACTH), cortisol, total and free triiodothyronine (T(3), fT(3)) and thyroxine (T(4), fT(4)) concentrations, and functional variables (heart rate (HR), respiratory rate (RR) and rectal temperature (RT)) in calm and temperamental Limousin young beef bulls. Exit velocity measurement was used to classify bulls' temperament as calm (group I: consisted of eight slowest bulls) and temperamental (group II: consisted of five fastest bulls). Calm subjects showed an increase of ACTH (P<0.05) and T(4) (P<0.01) concentrations after transportation compared with before transportation values. Temperamental subjects showed higher ACTH (P<0.01) concentrations before transportation, and lower T(4) (P<0.05) and fT(4) (P<0.001) concentrations after transportation than calm subjects. Related to functional variables, temperamental young beef bulls showed a decrease of RT (P<0.05) after transportation compared with before values, higher RT (P<0.001) before transportation, and higher HR (P<0.001) and RR (P<0.01) after transportation than calm subjects. Data obtained suggest that longer periods of transportation could minimise the magnitude and duration of the endocrine and functional responses to stress of young beef bulls; such responses probably decrease or disappear during transport, in accordance with animal temperament.