Space Allowance for Gestating Sows in Pens

Neither floor space in group-housed pregnant sows nor the stall environment was adequate for sow well-being, according to University of Illinois researchers studying behaviour, cortisol and immune responses. However, they remarked on the sows' abilities to evoke the appropriate responses needed to adapt to their environment.
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Different floor space allowances for dry, pregnant sows in pens were evaluated to determine the impacts of space on sow behaviour, immune and cortisol measures, according to J.L. Salak-Johnson and colleagues at the University of Illinois at Urbana-Champaign.

In their paper published in Journal of Animal Science, they explain that the experiment consisted of six replications (blocks 1 to 6; n=20 sows per group), and within each replicate, physiological measurements were recorded for two consecutive pregnancies. A total of 152 sows were measured at 1 gestation, and 65 of those sows were measured at the successive gestation (n=217).

Groups of five sows per pen were assigned to 1.4, 2.3, or 3.3 square metre of floor space per sow or of five sows in individual stalls (1.34 square metres).

Behaviour measures were standing, sitting, lying, walking, drinking, oral-nasal-facial (ONF), sham chewing and aggression. Immune traits included both descriptive and functional aspects and cortisol.

On day 90 (±5) of gestation, the occurrence of ONF behaviours increased from 03:00hr to 15:00hr and lying behaviour decreased from 07:00hr to 11:00hr for sows kept at 2.3 square metres each. Sows in stalls displayed more (P<0.05) ONF from 15:00hr to 23:00hr.

Standing, sitting, drinking, ONF and sham-chewing behaviours were affected by floor space. Sows in pens with 2.3 square metres each performed more ONF, and sows with 1.4 square metres each performed more sham chewing (P<0.05). Standing (P=0.05) and drinking (P=0.06) were increased but lying (P=0.06) was reduced for sows in pens at 2.3 or 3.3 square metres. Sows in stalls spent more time sitting and drinking but less time lying down than those in pens (P<0.01).

Immune traits were affected by treatment (P<0.05). Neutrophils were reduced and lymphocytes were increased, resulting in a reduced neutrophil:lymphocyte (N:L) ratio (P<0.05), for sows in pens at 3.3 square metres each. Natural killer cells were increased but lymphocyte proliferation was reduced for sows in pens at 1.4 square metres each (P<0.05). Sows in stalls had greater N:L ratio than sows in pens (P<0.05).

For sows in pens, linear and quadratic responses were detected for behaviour and immune traits. As floor space increased, walking and aggression increased. As floor space decreased, neutrophils, N:L ratio and natural killer cell increased but as floor space increased, lymphocyte proliferation increased.

On the basis of behavioural and physiological responses shown by sows in all four environments, the Urbana researchers said it is apparent that neither floor space nor stall environments provided adequate or quality of space to improve sow well-being. However, the differential behavioural and physiological mechanisms initiated by sows in response to their specific environment demonstrated that the sows were able to evoke the appropriate response(s) needed to adapt adequately to their environment.


Salak-Johnson J.L., A.E. DeDecker, M.J. Horsman and S.L. Rodriguez-Zas. 2012. Space allowance for gestating sows in pens: Behavior and immunity. J. Anim. Sci., 90(9):3232-3242. doi: 10.2527/jas.2011-4531

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October 2012
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