SOCIAL INFLUENCES ON THE REACTIVITY OF HEIFERS - IMPLICATIONS FOR LEARNING-ABILITIES IN OPERANT-CONDITIONING

The first experiment investigated the learning abilities of different types of heifers and the capacity of familiar conspecifics to reduce their behavioural reactivity. Two groups of 12-15 month-old Friesian and Aubrac (French breed) heifers were used. Ten animals of each breed were tested individually: 5 alone and 5 in the presence of the two other group mates. Heifers were trained daily, using an operant conditioning method, to press a panel (conditioned response) in order to obtain food. The number of trials necessary for the animals to learn the response was recorded. Their reactions towards the novel conditioning apparatus and pairing the food with a stressful stimulus were measured in the first phases of the conditioning procedure. In the absence of conspecifics, Aubrac heifers learnt more slowly than the other animals. At the onset of the conditioning test, they exhibited more signs of disturbance towards fear-eliciting stimulation. The differences in reaction between the two breeds were explained in terms of different levels of social attachment and novelty of the surroundings. A second experiment was conducted using the same conditioning procedure to repeat the first experiment and to assess the influence of affinity relationships with spectator conspecifics on the reactivity of heifers. Twenty-four 2-year-old Salers (French breed) heifers were tested: 8 alone and 16 others in the presence of two companions for which they had either a strong (8 animals) or a weak affinity (8 animals). The reactivity of each animal was assessed as previously in a novel environment and in an approach-avoidance conflict situation. As in the first experiment, the presence of peers improved the behavioural responsiveness towards the fear-inducing situations. Only one measure differentiated the subjects according to the social quality of the "spectator" companions: the time heifers spent feeding near the spectators was positively correlated with their affinity. The importance of the "spectator" companions' reactivity and the communication of stress is discussed. © 1990.