Does boar presence influence aggression, shoulder scratches and stress among newly mixed bred sows?

By M. J. Séguin, T.M. Widowski and R.M. Friendship, University of Guelph; R.N. Kirkwood and A.J. Zanella, Michigan State University - This article is taken from the University of Guelph Swine Research Review 2005 report. In group housing systems, the mixing of unfamiliar sows often results in aggression within the first few days which can cause injury and stress.
calendar icon 12 November 2005
clock icon 3 minute read


The use of boar pheromones or boar presence have been shown to reducing fighting among young pigs, weaned sows and slaughter-weight pigs, but any effect of boar presence on aggression among groups of newly mixed bred sows has not been previously reported.

Furthermore, there is no research documenting the impact of boar removal after hierarchy formation on the behaviour of group-housed sows.


  • To determine how different levels of boar presence affected aggression, shoulder scratches and acute stress response (stress hormone, cortisol) among newly mixed group-housed bred sows.

  • To determine the effect of boar removal one week later on these measurements.


Groups of 15 bred sows (2.3m2/sow) were mixed while exposed to one of three levels of boar presence (N=5 per trt): PHYSICAL (boar in pen with sows), FENCELINE (boar in pen next to sows) or CONTROL (no boar present in room). The boar was removed six days after mixing. During the 24h pre- and 24h post-mixing and boar removal the number of shoulder scratches were scored and saliva samples were collected twice daily. The frequency and duration of fights were collected from video-recordings.


  • PHYSICAL presence of the boar reduced scratches 24h post-mixing compared to CONTROL (P < 0.05).

  • The stress hormone, cortisol, was highest in the PHYSICAL treatment 24h post-mixing (0.41 ± 0.12 ng/mL ) compared to the FENCELINE (0.19 ± 0.04 ng/mL , P<0.05) and CONTROL (0.26 ± 0.03 ng/mL; P>0.10).

  • Frequency and duration of fighting were not affected by boar presence.

  • Removing the boar did not affect behaviour, scratches or stress response.

Take Home Message

There was no clear advantage of boar presence on reducing aggression or stress among newly mixed bred sows.

Source: Animal & Poultry Science University of Guelph - Reproduced September 2005

© 2000 - 2022 - Global Ag Media. All Rights Reserved | No part of this site may be reproduced without permission.