An investigation of the roles of boar-component stimuli in the expression of proceptivity in the female pig

Abstract

To examine the importance of visual, auditory and olfactory stimuli from the mature boar in eliciting proceptive behaviour in the mature female pig, 60 Large White × Landrace sows were randomly allocated to be tested for appetitive behaviour in T-maze preference tests. Various combinations of the boar-component stimuli (visual, auditory and/or olfactory cues) were presented to the sows as a choice in the arms of a T-maze. The relative attraction of the sows towards the various combinations of stimuli presented was interpreted as showing that these stimuli elicited proceptive behaviour in the sow. The proceptivity of the sows was assessed during oestrus (sexual receptivity), immediately after oestrus and during anoestrus (pregnancy). Analysis of the 928 T-maze preference tests carried out in this experiment indicated that visual cues from the boar were of primary importance in eliciting sow proceptivity during the oestrous period. However, when no visual cues were presented, olfactory stimuli from the boar became important in orientating the proceptive behaviour of the oestrous sow. Sows exhibited significant preferences for boars releasing androstene pheromones in saliva over boars unable to release salivary androstenes when neither boar could be seen. In the absence of both visual and olfactory stimuli, there was some evidence for the involvement of auditory cues from the boar in eliciting proceptive behaviour in the females. Proceptive behaviour was significantly related to the receptive state of the female at oestrus — declining during post-oestrus and rarely being exhibited significantly during anoestrus. It is suggested that deficiencies in olfactory stimuli (salivary androstenes) from the boar may be responsible for mate preferences exhibited by some sows under intensive husbandry conditions.