We hypothesised that a range of parasite doses that cause subclinical disease would lead to similar behavioural changes in cattle. This was tested by infecting bull calves with one of four different doses of the gastrointestinal parasite Ostertagia ostertagi: 0 (control), 75,000 (L), 150,000 (M) or 300,000 (H) larvae, whilst measuring aspects of their behaviour, usually encompassed by the term ‘sickness behaviour’. For parasitised bulls faecal egg counts and serum pepsinogen levels were elevated from Day (D) 20, the latter being affected linearly by dose. The different doses had different effects on animal fitness: body weight gain (BWG) was reduced for treatments M and H from D23, with M animals showing a recovery after D30, whereas H bulls continued to have lower BWG. Behaviours were only affected for H animals. Average lying episode duration increased by 25% and lying and standing episode frequency decreased by 22% from around D29 when compared to uninfected controls. The number of steps taken by H animals decreased by 34% relative to the controls from D34–46. There was no significant effect on any parameters of feeding behaviour. The results suggest that, for a wide range of parasite doses, general posture, activity and feeding behaviour may be unaffected despite some effects on host fitness. However, higher doses which may lead to clinical disease result in effects that are possibly directly related to pathogen dose. The practical applications of detecting health challenges through behaviour may therefore depend on the level of infection and their pathophysiological consequences.
|Publication Title||Applied Animal Behaviour Science|
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