title: Aggression and cortisol levels in three different group housing routines for lactating sows.
abstract: BACKGROUND
  Lactating sows in Swedish organic piglet production are commonly group-housed with piglets in a multi-suckling pen within 14 days after farrowing. Nursing behaviour may be disturbed when lactating sows are moved to a new environment and mixed with other sows, as they spend more time fighting with other sows and exploring the new surroundings. This can disrupt the inhibitory effect of suckling on ovarian activity and increase the risk of lactational oestrus, making efficient reproductive management difficult. Therefore this study evaluated aggression and levels of the stress hormone cortisol in lactating sows group-housed together with their piglets at one (W1), two (W2) or three (W3) weeks post farrowing.
  
  
  RESULTS
  There was no significant difference (P > 0.05) between the three management routines (W1, W2, W3) regarding number of attacks initiated or received in the mixed group. After mixing, W2 sows had a lower number of shoulder scratches (P < 0.05) than W3 sows. Among the W3 sows, there was a lower (P < 0.01) cortisol concentration in saliva when sows were group housed compared to when they were individually housed. The cortisol response, measured as variation in cortisol concentration in saliva, was also lower (P < 0.05) in group-housed W3 sows compared with W1 sows. For all management routines, sows already living in the new environment (resident sows) initiated more attacks (P < 0.001) and received fewer attacks (P < 0.01) than sows entering the new environment (intruder sows). Overall, multiparous sows initiated more attacks and received fewer attacks than primiparous sows (P <0.001).
  
  
  CONCLUSIONS
  Overall, the results suggest that mixing and group housing sows at three weeks post farrowing is less stressful than mixing and group housing sows at one week post farrowing. The results also indicate that parity and whether a sow is a resident or intruder in the group housing environment may have an effect on aggression levels when sows are group-housed.
authors.affiliation: Division of Reproduction, Department of Clinical Sciences, Swedish University of Agricultural Sciences, SLU, Box 7054, SE-750 07, Uppsala, Sweden. ola.thomsson@slu.se.
authors.forename: Ola
authors.initials: O
authors.lastname: Thomsson
authors.affiliation: Division of Reproduction, Department of Clinical Sciences, Swedish University of Agricultural Sciences, SLU, Box 7054, SE-750 07, Uppsala, Sweden. ann-sofi.bergqvist@slu.se.
authors.forename: Ann-Sofi
authors.initials: AS
authors.lastname: Bergqvist
authors.affiliation: Division of Reproduction, Department of Clinical Sciences, Swedish University of Agricultural Sciences, SLU, Box 7054, SE-750 07, Uppsala, Sweden. ylva.sjunnesson@slu.se.
authors.forename: Ylva
authors.initials: Y
authors.lastname: Sjunnesson
authors.affiliation: Swedish Animal Health Service, Kungsängens Gård, SE-753 23, Uppsala, Sweden. Lena-e-s@svhdv.org.
authors.forename: Lena
authors.initials: L
authors.lastname: Eliasson-Selling
authors.affiliation: Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, SLU, Box 7023, 750 07, Uppsala, Sweden. nils.lundeheim@slu.se.
authors.forename: Nils
authors.initials: N
authors.lastname: Lundeheim
authors.affiliation: Division of Reproduction, Department of Clinical Sciences, Swedish University of Agricultural Sciences, SLU, Box 7054, SE-750 07, Uppsala, Sweden. ulf.magnusson@slu.se.
authors.forename: Ulf
authors.initials: U
authors.lastname: Magnusson
mesh_terms: D000374:Aggression; D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D005260:Female; D006799:Housing, Animal; D006854:Hydrocortisone / Q000378:metabolism*; D007774:Lactation; D058871:Organic Agriculture; D012463:Saliva / Q000737:chemistry; D034421:Sus scrofa; D013548:Sweden
chemical_list: D006854:Hydrocortisone