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Keywords:

  • aggression;
  • mating;
  • pigs;
  • pheromones;
  • hormones;
  • olfaction

Abstract

Aggressive and sexual behaviour was studied in 5-min paired encounters between castrated prepubertal boars (N = 14) and normal (N = 2) or bulbectomized (N = 2) oestrogen-treated ovariectomized gilts. The boars were made sexually active by treatment with 17β-oestradiol + 5α-dihydrotestosterone. Half of the boars were sprayed on the snout with a solution containing a mixture of the boar pheromones 3α-androstenol and 5α-androstenone immediately before testing, and the remainder were treated with the vehicle solution. Aggression was almost always initiated by the gilts, and neither bulbectomy nor pheromone treatment of the boars reduced its occurrence. The results suggest that the display of aggression by gilts towards boars of similar body size is unlikely to be suppressed by the steroidal pheromones present in boar saliva.