Group and individual sow behavior is altered in early gestation by space allowance in the days immediately following grouping1

Abstract

Aggression between domestic sows is greatest when sows are first introduced to each other and hierarchies form. The aim of this study was to determine the effect of a spacious "mixing pen" on sow aggression and stress. Sows were mixed into groups of 6 and allowed 2 (LOW; 8 groups and 48 sows), 4 (MED; 7 groups and 42 sows), or 6 m/sow (HIGH; 7 groups and 42 sows) for 4 d after mixing, at which point all pens were equalized to 2 m/sow. Salivary cortisol concentration and injury counts were measured on d -1, 0, 1, 3, and 4 relative to mixing, and behavior was also recorded on each of these days following mixing. Reproductive performance was assessed at farrowing. A linear mixed model was applied to the data. Data are presented as least squares means and standard error of the mean. Where transformations occurred, nontransformed adjusted means are presented in parentheses following the presentation of transformed data. In the primary analyses where measures were considered at the pen level, there were no effect of space allowance on fight number per sow, duration of fights, percentage of total time spent fighting, displacements, bites, knocks, and lunges ( > 0.05). These measures were higher on d 0 (i.e., fight number 1.0 ± 0.1 [13.8]) compared with d 1 (0.4 ± 0.1 [4.2]), 3 (0.7 ± 0.1 [5.3]), and 4 (0.7 ± 0.1 [5.5]; < 0.05), with no increase in aggression on d 4 when pen sizes were standardized ( > 0.05). There was increased percentage of time spent active (1.5 ± 0.02 [33.7] for LOW, 1.5 ± 0.02 [36.5] for MED, and 1.6 ± 0.02 [43.4] for HIGH) and time spent exploring (1.8 ± 0.1 [3.5] for LOW, 2.0 ± 0.1 [4.0] for MED, and 2.3 ± 0.1 [5.7] for HIGH) and number of nonaggressive sow-sow contacts (0.3 ± 0.09 [2.2] for LOW, 0.4 ± 0.07 [3.2] for MED, and 0.5 ± 0.07 [4.5] for HIGH) in HIGH compared with LOW ( < 0.05). Farrowing rate and total piglets born were not affected by treatment ( > 0.05). A secondary analysis was conducted that examined individual sow behavior within each pen, and this identified increased injury number in the lowest ranked sows (involved in no fights on d 0 and no displacements on d0 to d4) in LOW (9.3 ± 1.2 [107.9] for LOW, 6.2 ± 0.8 [53.0] for MED, and 5.1 ± 0.8 [28.1] for HIGH) and also decreased fight number and duration in HIGH compared with LOW on d 0 and 1 ( < 0.05). Our primary data analysis demonstrates positive exploratory and social behaviors with increased space and suggests that a reduction in space following hierarchy formation is not a significant stressor. Additionally, there is some evidence at an individual sow level that increased space at mixing benefits sow welfare parameters, especially for low-ranked sows.

Feeding Strategies Before and at Mixing: The Effect on Sow Aggression and Behavior

“…As discussed previously, the sows in this piggery are accustomed to group housing and hierarchy formation, therefore may adjust more readily to group-housed situations [39], resulting in the saliva cortisol concentrations not being affected by mixing. The cortisol levels in this experiment are comparable to levels reported by Greenwood et al (2016), in the same piggery with similar genetics [31]. The overall effect of diet on aggression was limited.…”

“…Also, the non-aggression-based behaviors in this study showed that sows spent more time active and exploring, and therefore less time resting, in the early days after mixing, compared with day six post-mixing. Previous research on the same population found a similar reduction in aggression within 24 h [31], and a study by Moore et al (1993) saw a reduction in aggression as soon as 1 h following mixing [37]. Additionally, Hemsworth et al (2013) found that mixing stress in sows was most obvious soon after mixing, subsiding by days 8 and 9 [39].…”

Provision Point-Source Materials Stimulates Play in Sows but Does Not Affect Aggression at Regrouping

“…A modification of the assessment described by Karlen et al (2007) was used to describe lesion counts in all treatments [2]. Each side of the sow’s body was divided into 21 areas and the number of skin lesions in each area was counted [27,28]. Sows were also placed into an injury score group and given a rank from 0–5 based on the number of injuries; sows with 0–10 injuries were group 0; 11–20 were group 1; 21–30 were group 2; 31–40 were group 3; 41–50 were group 4; 50+ were group 5.…”

Behavioral and cortisol responses to feeding frequency in pregnant sows under isocaloric intake

“…Saliva samples were collected 1 hr before and after each feeding time and 3 hr after the last feeding occasion (i.e., 0630, 0830, 1030, 1230, 1430, 1630, and 1830 hours) using neutral synthetic swab Salivette (Sarstedt, Aktiengesellshaft and Co, Numbrecht, Germany) attached to cotton string. The string was hung in the stall to allow sows to chew on the Salivette until it became completely soaked with saliva ( Greenwood et al, 2016 ). Saliva samples were collected on ice and centrifuged 2 hr later at 2,500 × g for 10 min at 4 °C.…”