A ‘two-stage’ farrowing and lactation system: sow behaviour and injuries

Loose farrowing systems that meet the biological needs of the sow have been developed (Baxter et al. 2011). A ‘two-stage group lactation’ system, where the sow farrows in either a loose farrowing pen (e.g. PigSAFE system) or farrowing crate and is then moved into a group lactation (GL) system approximately 14 days after farrowing, is being investigated. The PigSAFE loose farrowing system allows visual and physical ‘fenceline social contact’ between sows which could maintain social bonds between sows and piglets and may reduce aggression and enhance maternal behaviour when mixed into group lactation systems. This experiment tested the hypothesis that sow behaviour and injuries would differ when sows are mixed into group lactation from either farrowing crates or a PigSAFE system.

A total of 360 mixed-parity sows (Large White x Landrace, PrimeGro™ Genetics) were studied over six time replicates. Sows were randomly allocated to one of four treatment groups: 1) Farrowing crates (FC): sows housed in farrowing crates until weaning; 2) GL_FC: sows housed in farrowing crates then moved into GL 14 days prior to weaning; 3) PigSAFE (PS): sows housed in the PigSAFE loose farrowing system until weaning; and 4) GL_PS: sows housed in the PigSAFE system then moved to GL 14 days prior to weaning. The housing treatments were located in three adjacent buildings with similar ventilation and construction material. The buildings were open-sided with shutters and heating which enabled some temperature control. All sheds were managed by the same stockpeople. Sows had access to an ad libitum feeder in the GL pen. The behaviour of the sows in GL_FC and GL_PS pens was recorded for 4 hours immediately after mixing and the day before weaning (from 0800 h) using HD Sports cameras. Aggressive behaviour (parallel pressing, head knocks and bites) was observed for 1 hour and suckling behaviour for 4 hours during the observation period, with all data recorded by one observer using a scan sampling technique. The time for the sow to first suckle a litter was recorded upon entry to the group lactation pens. Sow skin injury (assumed to be caused by aggression) was assessed on all sows according to Karlen et al. (2007) at 13 days before weaning (after mixing in the group lactation pens) and at weaning (25 ± 2.7 days; mean ± SD). The injury data were transformed prior to analysis. Univariate GLM analysis (IBM SPSS, Version 21.0; USA) was used to analyse the injury scores using each block of six FC, six PS and GL pens (6 sows/pen) as the experimental unit with replicate as a random factor in the design. An independent two-sided T-test was used for analysis of the behaviour data.

Fresh skin injuries were lower in sows housed in the FC and PS systems compared to either of the GL systems (Table 1). There was no difference in skin injuries or aggression between sows mixed into GL from either the FC or PS systems. Sows that had previously been housed in the PS pen showed a shorter latency to first suckle after mixing into GL (P < 0.05) compared to sows from the FC (35 vs 53 min. ± 5.4 min; mean ± SEM, GL_PS and GL_FC treatments, respectively). This suggests that aspects of sow behaviour immediately after mixing into GL can differ depending on the farrowing environment. Further research is warranted to fully assess the welfare of sows and piglets in GL systems, particularly the impact of age at mixing.

Table 1.  Average sow skin injuries in different housing treatments^B