INDIVIDUAL BEHAVIORAL-CHARACTERISTICS IN PIGS

In two identical experiments a total of 218 piglets from 20 sows were used to test if consistent individual behavioural differences exist am ong pigs. At an age of 1-2 weeks piglets were divided between aggressi ve and non-aggressive individuals on the basis of their behaviour in t wo successive social confrontation tests (SC1 and SC2). Substantial ag reement in this classification existed between the two observers and b etween SC1 and SC2. No significant sex and litter effects were found i n the occurences of aggressive behaviour. After mixing at 10 weeks and again at 15 weeks of age, aggressive behaviour was mainly shown by th e aggressive individuals as classified in the social confrontation tes ts. In a non-social backtest piglets, restrained in a supine position, were classified as resistant (R; more than two escape attempts), inte rmediate (I; two escape attempts) or non-resistant (NR; less than two escape attempts). Based on the outcome of five successive backtests in Weeks 1, 2 and 3 piglets were classified eventually as R (n = 95), NR (n = 7) or Doubtful (D; n = 46). R piglets had a shorter latency to f irst resistance, but a higher number of vocalizations than NR ones, wh ile the behaviour of the D piglets was in between. Piglets classified as R in the backtest were mostly the aggressive individuals, while NR piglets were mostly the non-aggressive ones; D piglets were equally di stributed over aggressive and non-aggressive individuals. This associa tion in behaviour and its consistency over time strongly suggests the existence of behavioural strategies to cope with conflict situations t hat are typical of individual pigs and are measurable already in the v ery first weeks of their life.