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 among pigs. At an age of 1-2 weeks piglets were divided between aggressive and non-aggressive individuals on the basis of their behaviour in two successive social confrontation tests (SC1 and SC2). Substantial agreement in this classification existed between the two observers and between SC1 and SC2. No significant sex and litter effects were found in the occurences of aggressive behaviour. After mixing at 10 weeks and again at 15 weeks of age, aggressive behaviour was mainly shown by the aggressive individuals as classified in the social confrontation tests. In a non-social backtest piglets, restrained in a supine position, were classified as resistant (R; more than two escape attempts), intermediate (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 first resistance, but a higher number of vocalizations than NR ones, while 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 distributed over aggressive and non-aggressive individuals. This association in behaviour and its consistency over time strongly suggests the existence of behavioural strategies to cope with conflict situations that are typical of individual pigs and are measurable already in the very first weeks of their life.