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Title: Group space allowance has little effect on sow health, productivity, or welfare in a free-access stall system

Author
item MACK, L - Purdue University
item Lay Jr, Donald
item Eicher, Susan
item JOHNSON, A - Iowa State University
item RICHERT, B - Purdue University
item PAJOR, E - University Of Calgary

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2014
Publication Date: 6/1/2014
Citation: Mack, L.A., Lay Jr., D.C., Eicher, S.D., Johnson, A.K., Richert, B.T., Pajor, E.A. 2014. Group space allowance has little effect on sow health, productivity, or welfare in a free-access stall system. Journal of Animal Science. 92(6):2554-2567.

Interpretive Summary: All gestational sow housing options present benefits and challenges. Standard gestation stalls create a welfare challenge by limiting sow locomotion and natural behavior, but are concurrently beneficial by limiting physically aggressive exchanges and allowing individualized feeding and care. Conversely, group housing increases behavioral freedom, but can result in greater physical aggression and reduced productivity. The free-access stalls are an alternative, hybrid housing system designed to protect sows from aggression and allow behavioral diversity. Additionally, these stalls give sows environmental control by allowing them to choose between stall protection or group space use which may benefit their welfare. In previous research using a preference test, sows strongly chose free access stalls over locked stalls irrespective of previous housing. This study’s main objective was to determine the effects of group space allowance in a free access stall system on gestating sow health, physiology, behavior, and productivity. We predicted that reduced group space allowance would result in increased aggression, injuries, and stress. Sows were housed in groups of 7 with either: 0.91 meter (small), 2.13 meter (intermediate), or 3.05 meter (large) alley ways behind the stalls which the sows could access. The group space allowance had no measurable impact on the health, physiology, or productivity of the sows. However, the lower group space use and social contact in the small pens may indicate greater social stress and reduce the behavioral diversity benefits of group housing. Free access stalls present an alternative housing system to standard gestation stalls and other forms of group housing; which producers may find useful for providing advantages of group housing yet also providing some advantages of stall housing.

Technical Abstract: Free-access stalls allow sows to choose the protection of a stall or use of a shared group space. This study investigated the effect of group space width: 0.91 (SS), 2.13 (IS), and 3.05 (LS) m on the health, production, behavior, and welfare of gestating sows. At gestational day (GD) 35.4 ± 2.3, 21 pregnant sows (N = 189) were distributed into 3 pens of 7 sows where they remained until GD 104.6 ± 3.5. Each treatment pen had 7 free-access stalls and a group space that together provided 1.93 (SS), 2.68 (IS), or 3.24 (LS) m2/sow. Baseline measurements were obtained prior to mixing. Backfat depth, BW, BCS, and lameness were measured monthly and skin lesions scored weekly. Blood was collected monthly for hematological, immunological, and cortisol analyses. Sow behavior was video recorded during the initial 4 d of treatment and every other week thereafter. Behavior was analyzed for location, posture, pen investigation, social contact, and aggression. Skin response to the mitogen concanavalin A (Con A) was tested at experimental day 70. Litter characteristics including size and weight were collected at birth and weaning. The data were analyzed using a mixed model (PROC GLIMMIX, SAS 9.2). Multiple comparisons were adjusted with the Tukey-Kramer method and the false discovery rate was controlled with the Bejamini-Hochberg method. Group space allowance had no effect on any measure of sow health, physiology, or production (P = 0.10). Sows in the SS, IS, and LS pens spent 77.88 ± 3.88, 66.02 ± 3.87, and 63.64 ± 3.91%, respectively, of their time in the free-access stalls (P = 0.12). However, SS sows used the group space less than IS and LS sows (P = 0.01). Overall, pen investigatory behavior was not affected by group space allowance (P = 0.91). Sows in the LS pens spent more time in a social group than SS sows (P = 0.02). Sows in IS pens were intermediate to, but not different than the other treatments (P = 0.10). The size of the social groups was also affected by the group space allowance (P = 0.03) with SS sows forming smaller groups than LS sows. Again, IS sows were intermediate to, but not different than the other treatments. The group space allowance had no measurable impact on the health, physiology, or productivity of the sows. However, the lower group space use and social contact in the SS pens may indicate greater social stress and reduce the behavioral diversity benefits of group housing.