Behavioural and physiological effects in sheep of a chronic stressor and a parasite challenge

Abstract

Mature Merino ewes, either at pasture (paddock) or in a feedlot situation (penned), were given a serial challenge infection with the gastric nematode parasite, Haemonchus contortus, and compared with control animals for their behaviour in an arena test, their plasma cortisol concentration and haematological and immunological status. Very low levels of infection resulted and parasitic disease was not evident. There were, however, significant effects on behaviour of both the challenge infection and the feedlot situation. The parasitic treatment resulted in a reduced distance between the sheep and the person in the arena test and also an increase in locomotor activity in the case of penned sheep. Overall, the penned animals displayed twice as much locomotor activity as paddock sheep. Mechanisms whereby a infectious challenge could affect sheep behaviour require further investigation.