Assessment of individual differences in behavioural reactions of heifers exposed to various fear-eliciting situations

Abstract

Consistency of individual variability in reactivity to a variety of fear-eliciting situations reflects the existence of an underlying psychological profile, currently labelled fearfulness, which can influence most fundamental behaviours. In farm conditions, fear-related reactions can lead to injuries or stress responses in animal, and waste of time or economic losses for the farmer. Nevertheless, fearfulness in farm animals has only been assessed in a limited range of situations and generally without any validation concerning the interpretation of the observed reactions. The aim of the present study was, first, to elaborate a set of experimental fear-eliciting situations for cattle in an attempt to interpret some reactions of the animals in terms of fear, and second, to examine the consistency of individual differences in reactions across these different test situations. Four tests, based on the presence of events classically reported to induce fear or anxiety, were designed. They consisted of exposure to a novel environment (i.e. open-field test), to a novel object, to food placed in an unfamiliar arena and to a surprise effect. Fourteen Friesian heifers were individually submitted to each of these tests. Rank order correlation coefficients were calculated between their reactions first within each of the tests and then across the different tests. The correlations within each test (except the open-field test) make it possible to interpret some behaviours as signs of fear. Furthermore, correlations between these tests show that the fear-related reactions are related (22% of all correlations being significant): the propensity for an individual to react excessively to a given test is thus related to its reactivity to another frightening event. Moreover, correlations between the fear-related reactions recorded in these previous tests and reactions observed in the open-field test suggest that behaviours involving inactivity (total duration of immobility and mean duration of immobility bouts) and inhibition (latencies to enter and to exit the test room) can be interpreted as expressions of fear in cattle exposed to an open-field test. The assessment of fear-related reactions in farm animals might be used to predict the individuals' ability to adapt to the constraints of husbandry and thus to improve the efficiency of production and possibly the animals' welfare.