Does housing influence maternal behaviour in sows?

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Does housing influence maternal behaviour in sows? Charlotte G.E. Grimberg-Henrici a,∗, Kathrin Büttner a, Christian Meyer b, Joachim Krieter a a b

Institute of Animal Breeding and Husbandry, Christian-Albrechts-University, Olshausenstr. 40, D-24098 Kiel, Germany Chamber of Agriculture of Schleswig-Holstein, Gutshof 1, D-24327 Blekendorf, Germany

a r t i c l e

i n f o

Article history: Received 14 October 2015 Received in revised form 1 April 2016 Accepted 4 April 2016 Available online xxx Keywords: Maternal behaviour Group-housing system Behavioural testing Lactating sows

a b s t r a c t Farrowing crates prevent sows during lactation from moving freely and interacting unrestrictedly with their piglets. The aim of this study was to compare sows during lactation in a group-housing system (GH; n = 23) and sows in a conventional single-housing system (SH; n = 24) with regard to their maternal behaviour. GH sows were only fixed in their pens three days ante partum until one day post partum. For the remaining amount of time they were able to choose between their home pen and a shared running area. Piglets were able to leave their pens on day five post partum. Data were collected in four batches with six sows in each housing system. All sows were observed in week 2 and week 4 of lactation in six successive tests concerning their maternal behaviour. The sows’ reaction to piglet distress calls, separation from and reunion with their piglets was tested both in their home pens and in a test arena for a maximum of five minutes. The test arena (3.9 m × 3.7 m) provided a piglet nest in a corner. The sows were only able to hear and smell their piglets. In the piglet scream test in the home pen, GH sows were more responsive to piglet screaming than SH sows. GH sows showed more body movements towards their screaming piglets and aggressiveness towards the experimenter (p < 0.05) as well as stronger postural reactions at the end of the test; i.e. standing (p < 0.05). However, in the piglet scream test in the test arena, SH sows remained near their handled piglet more frequently (p < 0.05) and vocalised more frequently (p < 0.05). Whereas, GH sows tended to explore the test arena more (p < 0.10). During the separation test in the home pen, no behavioural differences between GH and SH sows could be obtained. During the separation test in the test arena, all sows remained near the piglet nest with their piglets. Furthermore, SH sows walked more (p < 0.05), while GH sows explored the test arena more frequently (p < 0.05). In the reunion test in the home pen, GH sows tended to vocalise more frequently (p < 0.10). No behavioural differences could be found between GH and SH sows in the reunion test in the test arena. Regarding total piglet losses (e.g. crushing, underweight, runting, spay legs), GH sows had lower total losses compared to SH sows (p < 0.05). Furthermore, GH sows crushed fewer piglets than SH sows (p < 0.05). To conclude, GH sows showed stronger behavioural reactions in the home pen and SH sows in the test arena. Thus, the housing system has an effect on maternal behaviour. Further research is needed to obtain more information, if the significantly lower piglet losses of GH sows are related to the stronger maternal reactions in the home pens of these sows and to the housing conditions ante partum. © 2016 Elsevier B.V. All rights reserved.

1. Introduction Several studies under semi-natural conditions have shown that maternal behaviour in pigs has not changed in the process of domestication, meaning the animals need to express maternal behaviour for example in terms of nest building behaviour (Stolba ˇ et al., 2000; Damm et al., 2002). Furand Wood-Gush, 1989; Spinka thermore, maternal behaviour is very important for piglet survival

∗ Corresponding author. E-mail address: [email protected] (C.G.E. Grimberg-Henrici).

and growth, due to the fact that it reduces starvation and crushing. These are the most common reasons for piglet mortality, which are related to asphyxia and hypothermia (Pedersen et al., 2011). However, the expression of maternal behaviour can vary between ˇ sows (Spinka et al., 2000; Andersen et al., 2005). Several studies have shown that sows with lower piglet mortality rates expressed more nest building behaviour (Andersen et al., 2005; Wischner et al., 2009), were calmer during farrowing (Andersen et al., 2005) and were more careful during lying down movements (Burri et al., 2009). Furthermore, sows with fewer piglet losses performed more nose-to-nose contacts with their piglets when they changed posture (Andersen et al., 2005). Another important maternal

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characteristic of sows is their willingness to protect their piglets. Aggressive sows showed a stronger behavioural response to separation from their piglets and had also fewer piglet losses than less aggressive sows (Hellbrügge et al., 2008). Previous studies have shown that maternal characteristics are measurable. In the piglet scream test, the reaction of sows was tested when their piglets were handled and stimulated to scream (Grandinson et al., 2003; Hellbrügge et al., 2008; Meliˇsová et al., 2014). In the separation and reunion test, sows were observed when they were separated from their piglets and again reunited with their piglets (Pitts et al., 2002; Andersen et al., 2005; Hellbrügge et al., 2008). Key variables in the maternal behaviour of sows recorded in these tests were for example the responsiveness to piglet distress calls, restlessness and the amount of aggression (Hellbrügge et al., 2008). Additionally, in the separation test, a note was made of whether sows searched and called for their piglets (Pitts et al., 2002). The time that the sows spent with nosing, the latency until nursing and the length of nursing was recorded during the reunion of sows with their piglets (Pitts et al., 2002; Andersen et al., 2005). In present pig husbandry, the most common housing system of sows at farrowing and during lactation is the single-housing system with farrowing crates. In this system, sows are housed individually and are confined in crates during lactation. Single-housing systems limit the possibility of sows to move freely, to interact naturally with their piglets and to express unhindered maternal behaviour. Furthermore, no contact between other sows and their litters is possible. Solutions for more welfare for lactating sows are group-housing systems as ‘get-away’ systems, multi-suckling systems or a combination of these two systems, such as reviewed by van Nieuwamerongen et al. (2014). The group-housing system described by Bohnenkamp et al. (2013) is inspired by the natural rhythm of sows under semi-natural conditions (e.g. separation from the group ante partum, building a nest, leaving the nest post partum while piglets stay in the nest, returning to the group with the litter, social contacts with other sows and litters) (Jensen, 1986). To our knowledge, a combined analysis of the effect of housing conditions and maternal behaviour is underrepresented. Therefore, the aim of this study was to analyse the effect of group-housed and single-housed sows with regard to their maternal behaviour. Sows were tested in week 2 and 4 of lactation in their home pens and in a test arena with regard to their maternal reaction to piglet distress calls, separation from their piglets and reunion with their piglets.

2. Material and methods 2.1. Animals and housing The study was conducted on the Futterkamp agricultural research farm of the Chamber of Agriculture of Schleswig-Holstein over a period from May 2014 until September 2014. A total of 47 cross-bred (Large White × Landrace) multiparous sows were tested during lactation in a group-housing system (GH) and in a conventional, single-housing system (SH) with regard to their maternal behaviour. All sows assigned to the GH system were normally housed in the SH system. All litters were standardised to 13 piglets for each sow until two days post partum. The GH system was designed as described by Bohnenkamp et al. (2013). In the GH system, six sows were housed together (Fig. 1). Each sow had a single pen (1.8 m × 2.6 m) provided with a farrowing crate and electronically controlled gates. In addition, all sows shared a running area (2.4 m × 5.4 m). The sows were only fixed in the farrowing crates three days ante partum until one day post partum. A flat barrier prevented the piglets from leaving the single pen, whereas the sow could continue to leave the pen. The barrier was removed five days

post partum and all litters of the six sows had the possibility to mix in the running area. GH sows were fed by hand in their pens. Sows in the SH system were fixed in farrowing crates (2.0 m × 2.6 m). SH sows were fed electronically. Sows in both housing systems were fed a commercial lactating meal which increased constantly during lactation to a maximum of 7.5 kg per day (divided into three to four meals). The piglets received a commercial creep diet. Both housing systems had water-heated piglet resting areas (0.6 m2 ) and manipulable material (e.g. plastic balls) was available for the sows and the piglets. The temperature varied in the two housing systems between 19 and 21 ◦ C. Lights (80 lx) were switched on at 6 am and off at 8 pm. In both housing systems, sows and piglets shared a drinking bowl and had free access to water. Boars were not castrated and the piglets were weaned on average 27.8 ± 0.15 days post partum. Data were collected in four batches with six sows per batch in each housing system. During gestation all sows were housed in a dynamic group with electronic feeding stations and were randomly moved to the GH or SH system, respectively, one week before the calculated farrowing date. When the sows did not farrow on the calculated date, the birth was initiated with an injection of Prostaglandin F2 ␣. The birth of 37 sows out of 47 sows was initiated. The sows farrowed on average 0.8 ± 0.15 days later as the before calculated date. The sows did not differ significantly concerning their number of parities between the two housing systems (GH: 5.3 ± 0.47 vs. SH: 4.9 ± 0.40 (n.s.)) and within the batches (batch 1: GH 3.8 ± 0.91 vs. SH 3.5 ± 0.56 (n.s.); batch 2: GH 6.0 ± 0.68 vs. SH 6.0 ± 0.68 (n.s.); batch 3: 6.8 ± 1.16 vs. SH 5.5 ± 0.92 (n.s.); batch 4: GH 4.8 ± 0.79 vs. SH 4.6 ± 0.80 (n.s.)). 2.2. Recorded traits Before the sows were moved to the GH and SH systems, all sows were weighed, their back fat (BF) was measured and their body condition score (BCS) was recorded (7.8 ± 0.15 days ante partum). The BF thickness (emaciated: <10 mm; thin: 11–15 mm; ideal: 16–18 mm; fat: 19–22 mm; overly fat > 22 mm) was measured with an ultrasound scanner (Agroscan, Hauptner & Heberholz, Solingen, Germany) 5 cm from the median line behind the shoulder, in the middle of the back and before the hip (Bohnenkamp et al., 2013). The mean of these three measurement points formed the BF value for each sow. The BCS ranged from 1 to 5 (1: emaciated (hips, spine prominent to the eye); 2: thin (hips, spine easily felt without pressure); 3: ideal (hips, spine felt only with firm pressure); 4: fat (hips, spine cannot be felt); 5: overly fat (hips, spine heavily covered)). After weaning (27.8 ± 0.15 days post partum), the same parameters were measured again for each sow. Furthermore, reproduction traits were documented as the number of piglets born alive, stillborn piglets, weaned piglets, piglet losses and individual weights of the piglets one day after birth and at weaning. Piglet losses were recorded during the whole lactation period regarding cause, date, weight of the piglet and location of the dead piglet for the GH system (home pen or shared running area). Total piglet losses included piglets that were crushed and piglets that died due to other reasons (e.g. underweight, runting, splay legs). 2.3. Behavioural testing All sows from both housing systems were tested in six different successive tests to investigate their maternal behaviour. The sows were observed in behavioural tests in week 2 (12.8 ± 0.15 days post partum) and in week 4 (25.8 ± 0.15 days post partum) of lactation (Fig. 2). The tests were performed in the home pens (HP) of the sows and in a test arena (TA). The TA was built to create a test situation for the sows, which was uncoupled from their housing environment. Thus, the TA was a similar and new environment

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Fig. 1. Schematic view of the two housing systems. The group-housing (GH) system with six individual pens (4.7 m2 ) and running area (13 m2 ). The single-housing (SH) system with individual pens (5.2 m2 ).

Fig. 2. Schematic view of time line for maternal testing in the home pen (HP) and in the test arena (TA).

for all sows. The tests started at 8 am and all sows were tested in a random order in each housing system. It was blocked by treatment with a random order for the sows. The TA was in a separate room. Because of logistical issues each housing system had its own TA. These TAs had the same design and dimensions. The TA was 3.9 m × 3.7 m large and the non-transparent side walls were 1.1 m high (Fig. 3). The entrance for the sow was 1.2 m wide and there was a piglet nest equipped with a heat lamp in one corner. The nest was 1.5 m × 1.5 m × 2.12 m large and the non-transparent side walls were 1.1 m high. The front wall of the nest had a door (0.8 m wide and 0.4 m high) and was connected with the inside of the TA. The TA was divided into four parts (painted on the floor) with four possible localisations of the sows.

2.3.1. Piglet scream test in home pen In the first test, the reaction of the sow to distress calls from her whole litter by catching them was observed. The test was modified according to the experiment by Held et al. (2006). The test showed the willingness of the sow to protect her piglets. Furthermore, the test investigated the sow’s reactivity and responsiveness to piglet distress calls. The piglet distress call was an intensive sound with a high frequency and was used to simulate a piglet in great need (Andersen et al., 2005). Before the test started, GH sows and their piglets were confined in their own HP. Two experimenters caught the piglets and put them in a transport carriage while one of these experimenters documented the posture of the sow before the test started and the posture of the sow when the last piglet was put in the transport carriage. The posture of the sow could have

two possible dimensions, standing or touching the floor with her body (sitting, kneeling and lying). Standing was scored as strongest postural reaction of the sow. Furthermore, the sow’s vocalisation (yes/no) was also noted and the maximum behavioural response of the sow was evaluated in form of a behavioural grade at the end of the test 0—no reaction; 1—weak reaction (head movement towards screaming piglets); 2—medium reaction (body movement towards screaming piglets); 3—strong reaction (attack towards experimenter). One observation per sow and test was documented with regard to posture and behavioural grade. During this test, one piglet was separated for the piglet scream test in the TA, which was performed later in the experimental setup.

2.3.2. Separation test in test arena After the piglet scream test, the sow was brought to the TA. The sow had ten minutes to habituate to the new environment. After the habituation, the piglets were transported to the TA and were put in the piglet nest in the corner. When the first piglet was put in the piglet nest, the separation test started. The sow was able to hear and smell her piglets. The sow was observed every ten seconds for a whole observation period of five minutes (31 observations per sow and test) concerning localisation in the TA (Figure 3), posture, behaviour and vocalisation (Table 1). The test design was modified according to previous experiments by Pitts et al. (2002) and Andersen et al. (2005). The test showed how focused the sow was towards her piglets during separation and investigated the responsiveness of the sow to her piglets. Behaviour was preferred which was directed towards the piglets such as vocalisation, occupation

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Fig. 3. Schematic view of the test arena (TA).

Table 1 Ethogram for behavioural observation in the tests in the home pen (HP) and in the test arena (TA) (modified according to Pitts et al. (2002) and Andersen et al. (2005)). Variable

Behaviour

Location

Description

Posture

Active Inactive Active Inactive Exploring floor Exploring nest

HP HP TA TA HP/TA TA

Exploring TA

TA

Contact

HP/TA

Vocalisation

HP/TA

Sow stands or kneels down. Sow sits or lies. Sow walks or kneels down. Sow stands, sits or lies. Sow sniffs or roots with the nose within 0.2 m of the floor. Sow explores with her nose or scratches with her front legs the front wall of the piglet nest in the TA. Sow sniffs or roots with the nose within 0.2 m of the floor and explores with her nose or scratches with her front legs the side walls of the TA. Sow has contact with her nose with a piglet or searches for contact by running after a piglet. Any vocalisation by the sow.

Behaviour

Vocalisation

with the piglet nest, staying near the piglet nest and stress signals such as restlessness.

2.3.3. Reunion test in test arena After the separation test, the reunion test was performed. For this, the door of the piglet nest was opened to reunite the sow with her piglets. The test started when the door was opened. The piglets were carefully pushed with a broom to leave the nest. When all piglets had left the nest, the door was closed. The reaction of the sow was recorded again every ten seconds for an observation period of five minutes (31 observations per sow and test) with regard to localisation (Fig. 3), posture, behaviour and vocalisation (Table 1). This test was a modified version of the test by Pitts et al. (2002) and Andersen et al. (2005). The reaction of the sow to her piglets was tested when the piglets were suddenly present. Behaviour which focused on the piglets such as nose-to-nose contact with the piglets, running after the piglets, nursing and vocalisation were evaluated as good maternal behaviour.

2.3.4. Piglet scream test in test arena For the piglet scream test, the previously separated piglet was now taken to the TA where the sow with the rest of her piglets was walking around. One experimenter stood with the piglet outside the TA next to the piglet nest (localisation 1) and motivated the piglet to scream by placing it in a back position. The reaction of the sow was observed again every ten seconds for 30 s (four observations per sows and test) with regard to localisation (Fig. 3), posture, behaviour and vocalisation (Table 1). This test was similarly constructed compared to the experiments of Grandinson et al. (2003). According to the piglet scream test in the HP, this test investigated the willingness of the sow to protect her piglets and the reactivity and responsiveness of the sow to a piglet distress call. The behaviour was scored as good maternal behaviour when the sow turned towards her piglet using vocalisation, by staying near the screaming piglet and by getting in contact with her other piglets.

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2.3.5. Separation test in home pen After the tests in the TA, the sow returned to her empty HP, i.e. without her piglets. The observation started immediately when the sow had reached the empty HP (Pitts et al., 2002). The behaviour of the sow, posture and vocalisation was recorded every ten seconds for five minutes (31 observations per sow and test) (Table 1). The aim of this test was to investigate whether the sow had searched for her piglets. Searching and stressed behaviour was restlessness such as standing postures, exploring the floor for piglets and vocalisation.

Table 2 Least square means (LSM) and standard error (SE) of the reproductive traits of grouphoused (GH) and single-housed (SH) sows. GH (n = 23)LSM ± SE Piglets born alive/sow Stillborn piglets/sow Individual birth weight (kg) Total piglet losses/sow Crushed piglets/sow Piglets weaned/sow Individual weaning weight (kg) a−b

2.3.6. Reunion test in home pen The piglets were then transported from the TA to their HP and were placed with the sow. The observation started when the first piglet was placed in the pen (Pitts et al., 2002). The behaviour of the sow, posture and vocalisation were recorded every ten seconds for five minutes (31 observations per sow and test) (Table 1). Similar to the reunion test in the TA, the reaction of the sow was observed when her piglets were suddenly placed in the HP. Caring behaviour as nursing, nose-to-nose contacts and vocalisation of the sow was evaluated as good maternal behaviour. 2.4. Statistical analysis All data were analysed with the statistical software SAS® 9.2 (SAS Institute Inc., 2008). The MIXED procedure was used for data with normal distribution. The GLIMMIX procedure was applied for count data (poisson-distribution) and binomial data. Fixed effects were added in a stepwise manner to the model. The Akaike’s information criteria corrected (AICC) and the Baysian information criteria (BIC) were used to compare the different models. The model with the smallest AICC and BIC values was chosen. The data of the reproductive traits (birth and weaning weight of the piglets, number of piglets born alive, stillborn, weaned, crushed piglets and total piglet losses) and the BW, BCS and BF thickness of the sows were analysed with the MIXED procedure. The mixed model included the fixed effects housing (GH, SH), batch (1, 2, 3, 4) and parity class (class 1: 2, 3; class 2: 4–6; class 3: >6). The interaction between the fixed effects group and batch was tested and was removed because of no significant effects and no improved goodness of the fit criteria. The sow was added as random effect nested in group and batch to the model of birth weights and weaning weights. In addition, the model for the weaning weights was added with the birth weights and the lactation length as linear continuous variables. The model of BW, BCS and BF thickness post partum was completed with the BW, BCS and BF thickness ante partum as linear continuous variables. The significance of differences in the least square means was adjusted with the Bonferroni-correction. The count data of the behavioural tests (separation test in TA, reunion test in TA, piglet scream test in TA, separation test in HP, reunion test in HP) were analysed using the GLIMMIX procedure with a poisson-distribution with the log link function. For localisation 2, 3, 4 in the TA only few observation were found and were combined for analysis purposes as one localisation 234. The model included the fixed effects housing (GH, SH), batch (1, 2, 3, 4), parity class (class 1: 2, 3; class 2: 4–6; class 3: >6) and week (2, 4). The interaction between the fixed effects group and batch was tested and was removed because of no significant effects and no improved goodness of the fit criteria. The sow was added to the model as random effect nested in group and batch. The significance of differences in the least square means was adjusted with the Bonferroni-correction. The binomial data of the piglet scream test in the HP were analysed using the GLIMMIX procedure with a binomial distribution with the logit link function. For the behavioural grades 0 and 3 only few observations were documented and for analysis purposes the

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16.6 ± 0.74 1.1 ± 0.28 1.3 ± 0.04 1.8a ± 0.32 0.6a ± 0.27 12.5 ± 0.12 7.6 ± 0.15

SH (n = 24)LSM ± SE 15.7 ± 0.73 1.7 ± 0.28 1.3 ± 0.04 2.9b ± 0.32 1.5b ± 0.26 12.2 ± 0.12 7.8 ± 0.15

Significant differences between GH and SH sows (p < 0.05).

behavioural grades of 0 and 1 were combined to grade 1 (no to weak reaction) and the grades 2 and 3 were combined to grade 2 (medium to strong reaction). The model included the fixed effects housing (GH, SH), batch (1, 2, 3, 4), parity class (class 1: 2, 3; class 2: 4–6; class 3: >6) and week (2, 4). The interaction between the fixed effects group and batch was tested and was removed because of no significant effects and no improved goodness of the fit criteria. The sow was added to the model as random effect nested in group and batch. The significance of differences in the least square means was adjusted with the Bonferroni-correction. 3. Results 3.1. Reproductive traits Table 2 shows the results for the reproductive traits of GH and SH sows. The traits total piglet losses and crushed piglets differed between the two housing systems. The total percentage of the piglet losses during lactation was 10.7 % for GH sows and 18.3 % for SH sows. 69.7 % of all piglet losses from both housing systems occurred at birth and the first day post partum (GH: 67.5 % vs. SH: 70.6 %). The sows from the GH system had significantly lower total piglet losses at birth and the first day post partum (GH: 1.2 ± 0.30 vs. SH: 2.1 ± 0.30; p < 0.05) and during the whole lactation (GH: 1.8 ± 0.32 vs. SH: 2.9 ± 0.32; p < 0.05). 52.8 % of all piglets died due to crushing. Thereof, 66.6 % of these piglets were crushed within the day at birth and the first day post partum. Sows from the GH system crushed at birth and the first day post partum (GH: 0.2 ± 0.22 vs. SH: 1.1 ± 0.22; p < 0.05) and during the whole lactation (GH: 0.6 ± 0.27 vs. SH: 1.5 ± 0.26; p < 0.05) significantly lower piglets compared to sows from the SH system. The number of crushed piglets was marginal influenced by the parity class. Sows from parity class 3 crushed marginally more piglets compared to sows from the parity class 1 (class 1: 0.5 ± 0.35 vs. class 2: 1.0 ± 0.30 vs. class 3: 1.7 ± 0.40; p = 0.0960). Other causes that led to piglet mortality such as being underweight, runting, splay legs etc. were greater for GH sows than for SH sows (GH: 65.9 % vs. SH: 50.7 %; n.s.). Furthermore, the parity class 2 and 3 had more still born piglets compared to parity class 1 (class 1: 0.3 ± 0.38; class 2: 1.5 ± 0.32; class 3: 2.3 ± 0.41; p < 0.05). Sows from the parity class 1 weaned heavier piglets compared to sows from the parity class 2 and 3 (class 1: 8.1 ± 0.19 vs. class 2: 7.4 ± 0.17 vs. class 3: 7.76 ± 0.22; p < 0.05). 3.2. Body condition The BW, the BCS and BF thickness of the sows were compared ante partum (7.8 ± 0.15 days before farrowing) and post partum (27.8 ± 0.15 days after farrowing) between the two housing systems. GH sows and SH sows did not differ statistically concerning these body condition parameters (Table 3). On average, SH sows were slightly heavier ante partum (GH: 268.3 ± 4.44 vs. SH: 272.3 ± 4.38; n.s.) and post partum (GH: 231.0 ± 2.75 vs. SH: 236.3 ± 2.36; n.s.) compared to GH sows. The BW dif-

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Table 3 Least square means (LSM) and standard error (SE) of body weight (BW), body condition score (BCS) and back fat (BF) thickness of group-housed (GH) and single-housed (SH) sows. GH week 1 ante partum LSM ± SE Body weight (kg) Body condition score Back fat thickness (mm)

268.3 ± 4.44 3.44 ± 0.05 14.9 ± 0.56

(n = 23)

SH

week 4 post partum LSM ± SE 231.0 ± 2.75 2.9 ± 0.08 12.1 ± 0.37

fered significantly between the three parity classes ante partum (class 1: 250.9 ± 5.79 kg vs. class 2: 269.3 ± 4.95 kg vs. class 3: 290.7 ± 6.23 kg; p < 0.05) and post partum (class 1: 214.4 ± 3.95 kg vs. class 2: 226.9 ± 3.06 kg vs. class 3: 249.3 ± 4.31 kg; p < 0.05). The BCS of sows from the parity class 1 was lower than the BCS of sows from the parity class 2 and 3 post partum (class 1: 2.7 ± 0.08 vs. class 2: 2.9 ± 0.07 vs. class 3: 3.0 ± 0.09; p < 0.05). Furthermore, the BF thickness of sows from the parity class 3 was thicker compared to sows from the parity class 1 and 2 post partum (class 1: 11.8 ± 0.41 mm vs. class 2: 12.3 ± 0.36 mm vs. class 3: 13.5 ± 0.45 mm; p < 0.05). 3.3. Behavioural testing Table 4 shows the results of count data of the different behavioural maternal tests. The results of the piglet scream test in the HP are shown in the text. All tests are explained in more detail below. 3.3.1. Piglet scream test in home pen GH sows were obviously more responsive to the piglet scream test in the HP. 80% of GH sows received higher behavioural grades in the categories medium to strong reaction (body movements towards their piglets and aggressiveness towards the experimenter) compared to 40% of SH sows when catching their piglets (GH: 0.8 ± 0.08 vs SH: 0.4 ± 0.10; p < 0.05). In addition, at the end of the piglet scream test, 80% of GH sows showed stronger postural reactions, i.e. standing postures (GH: 0.8 ± 0.08 vs SH: 0.4 ± 0.10; p < 0.05). 3.3.2. Separation test in test arena SH sows were more active, i.e. walking, during separation from their piglets in the TA (GH: 5.5 ± 0.61 vs. SH: 8.0 ± 0.82; p < 0.05), whereas GH sows explored more the TA (GH: 7.0 ± 1.32 vs. SH: 3.4 ± 0.72; p < 0.05). Sows from both housing systems were near their piglets more frequently than in the rest of the TA (localisation-rest) during testing (GH: 20.2 ± 1.37 vs. 7.8 ± 1.63; SH: 21.9 ± 1.37 vs. 5.5 ± 1.17). Furthermore, they volcalised more (week 2: 21.0 ± 1.73 vs. week 4: 18.2 ± 1.52; p < 0.05) and explored the TA less frequently in week 2 than in week 4 of lactation (week 2: 4.5 ± 0.64 vs. week 4: 5.7 ± 0.80; p < 0.05). 3.3.3. Reunion test in test arena SH sows were more frequent in localisation 1 than GH sows during the reunion test in the TA (GH: 9.5 ± 0.84 vs. SH: 12.3 ± 0.78; p < 0.05). Sows from both housing systems were more active (week 2: 11.4 ± 0.70 vs. week 4: 8.3 ± 0.55; p < 0.05), vocalised more (week 2: 11.4 ± 1.50 vs. week 4: 4.7 ± 0.65; p < 0.05) and had more frequent contact with their piglets in week 2 compared to week 4 of lactation (week 2: 14.6 ± 0.70 vs. week 4: 8.6 ± 0.49; p < 0.05). Furthermore, both groups explored the TA more in week 4 compared to week 2 (week 2: 10.3 ± 0.58 vs. week 4: 15.4 ± 0.78; p < 0.05). Regarding the different parity classes, sows from the parity class 3 were less active (class 1: 10.9 ± 1.09 vs. class 2: 10.8 ± 0.92 vs. class 3: 7.8 ± 0.89; p < 0.05) and vocalised more compared to the parity

week 1 ante partum LSM ± SE 272.3 ± 4.38 3.43 ± 0.05 15.0 ± 0.55

(n = 24) week 4 post partum LSM ± SE 236.0 ± 2.72 2.9 ± 0.06 12.9 ± 0.28

classes 1 and 2 (class 1: 5.1 ± 1.25 vs. class 2: 6.2 ± 1.31 vs. class 3: 12.4 ± 3.15; p < 0.05). 3.3.4. Piglet scream test in test arena SH sows remained near their piglets (localisation 1) significantly more frequent (GH: 2.0 ± 0.21 vs. SH: 2.8 ± 0.25; p < 0.05) and vocalised more compared to GH sows during the piglet scream test in the TA (GH: 1.8 ± 0.23 vs. SH: 2.6 ± 0.29; p < 0.05), whereas, GH sows tended to explore the TA more (GH: 1.0 ± 0.22 vs. SH: 0.6 ± 0.14; p < 0.10). Furthermore, sows of both housing systems vocalised more (week 2: 2.5 ± 0.26 vs. week 4: 1.9 ± 0.22; p < 0.05), explored the TA less (week 2: 0.5 ± 0.12 vs. week 4: 1.0 ± 0.19; p < 0.05) and had more contact with their piglets in week 2 compared to week 4 of lactation (week 2: 0.8 ± 0.13 vs. week 4: 0.4 ± 0.09; p < 0.05). 3.3.5. Separation test in home pen No behavioural differences could be observed between GH and SH sows during reunion with their piglets in their HP. Sows from both housing systems were more active (week 2: 21.6 ± 1.45 vs. week 4: 19.4 ± 1.27 1.31; p < 0.05), vocalised more (week 2: 8.8 ± 1.86 vs. week 4: 6.0 ± 1.28; p < 0.05) and explored the floor more frequently in week 2 compared to week 4 of lactation (week 2: 8.9 ± 0.78 vs. week 4: 6.8 ± 0.63; p < 0.05). 3.3.6. Reunion test in home pen GH sows tended to call more frequently their piglets during reunion in the HP compared to SH sows (GH: 15.3 ± 1.78 vs SH: 11.3 ± 1.32; p = 0.0727). Sows from both housing systems were more active (week 2: 9.7 ± 1.50 vs. week 4: 7.2 ± 1.12; p < 0.05) and vocalised more frequently in week 2 compared to week 4 of lactation (week 2: 15.8 ± 1.35 vs. week 4: 11.0 ± 0.97; p < 0.05). Furthermore, both groups had more contacts with their piglets (week 2: 7.1 ± 0.49 vs. week 4: 5.6 ± 0.42; p < 0.05) and nursed their piglets more frequently in week 2 compared to week 4 of lactation (week 2: 3.0 ± 0.94 vs. week 4: 1.4 ± 0.47; p < 0.05). 4. Discussion 4.1. Reproductive traits In the present study sows housed in the GH system had significantly lower total piglet losses and crushed fewer piglets than SH sows. Two thirds of the total piglet losses of both housing systems occurred at birth and at the first day post partum. Previous research conducted in these two housing systems found no significant differences with regard to total piglet losses of GH and SH sows and they reported on more crushed piglets of GH sows, however, this was not statistically confirmed (Bohnenkamp et al., 2013). The design and the management of the GH system were not altered between the study of Bohnenkamp et al. (2013) and the present study. In the study of Bohnenkamp et al. (2013) an explanation for more crushed piglets in the GH system was that the pens of GH sows were smaller (0.52 m2 ) and, thus, the piglets had less space to react to posture changes of the sow. Li et al. (2010) reported lower piglet mortality rates in a GH system over several years. Here, an explanation was

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Table 4 Least square means (LSM) of the frequencies of the count data with standard error (SEM) and the percentage (%) of behavioural observations of group-housed (GH) and single-housed (SH) sows tested in week 2 and 4 of lactation and behavioural observations of all sows for week 2 and week 4 tested in the separation test in the test arena (TA), reunion test in the TA, piglet scream test in the TA, separation test in the home pen (HP) and reunion test in the HP. Test

Variable

GH

(n = 23)

LSM ± SEM Separation test in TA 5 min observation (31 observations per sow)

Reunion test in TA 5 min observation (31 observations per sow)

Piglet scream test in TA 30 s observation (4 observations per sow)

Separation test in HP 5 min observation (31 observations per sow) Reunion test in HP 5 min observation (31 observations per sow)

a–b c–d

Localisation 1 Localisation 234 Active Inactive Vocalisation Exploring TA Exploring nest Localisation 1 Localisation 234 Active Inactive Vocalisation Exploring TA Contact Localisation 1 Localisation 234 Active Inactive Vocalisation Exploring TA Contact Active Inactive Vocalisation Exploring floor Active Inactive Vocalisation Contact Nursing

20.2 ± 1.37 7.8 ± 1.63 5.5a ± 0.61 25.1a ± 0.74 18.9 ± 2.14 7.0a ± 1.32 6.9 ± 0.70 9.5a ± 0.84 21.7a ± 0.73 0.9 ± 0.72 21.2 ± 0.78 6.0 ± 1.12 13.3 ± 0.84 11.6 ± 0.69 2.0a ± 0.21 1.9a ± 0.27 1.3 ± 0.17 2.7 ± 0.24 1.8a ± 0.23 1.0c ± 0.22 0.5 ± 0.11 20.9 ± 1.89 4.8 ± 1.83 9.8 ± 2.89 8.4 ± 0.98 10.0 ± 2.14 16.9 ± 2.27 15.3c ± 1.78 6.8 ± 0.57 2.6 ± 1.20

SH

(n = 24)

LSM ± SEM

% 66.9 33.1 18.5 81.5 66.9 28.4 23.3 29.7 70.3 31.5 68.5 30.4 44.5 39.8 50.5 49.5 32.6 67.4 47.3 29.4 15.8 71.0 29.0 46.7 29.9 39.2 60.8 55.6 22.6 24.3

21.9 ± 1.46 5.5 ± 1.17 8.0b ± 0.82 22.4b ± 0.69 20.2 ± 2.25 3.4b ± 0.72 8.6 ± 0.83 12.3b ± 0.78 18.6b ± 0.66 10.3 ± 0.79 20.0 ± 0.74 9.0 ± 1.63 11.9 ± 0.76 10.8 ± 0.64 2.8b ± 0.25 1.1b ± 0.18 1.1 ± 0.16 2.8 ± 0.25 2.6b ± 0.29 0.6d ± 0.14 0.5 ± 0.10 20.0 ± 1.79 2.9 ± 1.17 5.4 ± 1.61 7.3 ± 0.84 6.9 ± 1.49 17.9 ± 2.38 11.3d ± 1.32 5.8 ± 0.50 1.5 ± 0.71

week 2(n = 47)

week 4(n = 47)

%

%

%

72.8 27.2 27.3 72.7 70.7 17.1 29.0 39.7 60.4 35.7 64.3 43.6 40.9 36.8 71.4 28.7 29.2 70.8 67.2 17.2 15.1 69.2 30.8 35.6 25.7 34.0 66.0 40.9 19.6 17.4

70.7 29.3 23.1 76.9 73.6 20.0 26.5 34.9 65.1 39.1 61.0 52.5 34.2 48.2 61.7 38.3 34.6 65.4 65.4 16.0 21.3 73.9 26.1 48.7 31.4 42.1 57.9 56.7 23.47 27.87

69.1 30.9 22.9 77.1 64.0 25.3 25.9 34.7 65.3 28.2 71.8 21.8 51.1 28.3 60.6 39.4 27.1 72.9 49.5 30.3 9.6 66.3 33.7 33.4 24.2 31.0 69.1 39.7 18.7 13.7

Significant differences between GH and SH sows (p < 0.05). Marginal differences between GH and SH sows (p < 0.10).

that the stockpersons had improved their skills in the course of time with regard to better observation and handling of the sows and, thus, had acquired a better approach to detecting problems. When the present study started, the GH system had already been implemented on the research farm for five years. The experience of the stockpersons could have had an effect on the piglet mortality rates in the present study. Furthermore, the sows in the GH systems were only fixed for three days ante partum and one day post partum, whereas, SH sows were fixed the whole time ante partum and post partum. GH sows had four days of free movement before farrowing. This time of free movement could probably have an influence on the physically and psychologically balance of the GH sows around farrowing. Lower piglet mortality rates are associated with sows that are calmer during farrowing (Andersen et al., 2005) and sows that are more careful during lying down movements (Burri et al., 2009). Further research could investigate if results were comparable when the sows of both housing systems were confined directly when they moved to the farrowing stable. Furthermore, in the present study a tendency was found that older sows crushed more piglets than younger sows. A reason for more piglet losses due to crushing by older sows could be the bigger size of the sows. A high incidence of more crushed piglets of sows from higher parity classes were also found in a study from Weary et al. (1998). No differences were found between GH and SH sows with regard to other reproductive traits. These results are in accordance with previous research, except for the individual weaning weight of the piglets, which was significant lower for the piglets in the GH system in the study of Bohnenkamp et al. (2013). Here, the lower weaning weight of piglets from GH sows was explained by the greater amount of missed nursings and playful behaviour of these piglets.

In the present study no differences concerning the weaning weight of the piglets were found. Creep feed was offered in both housing systems directly three days after birth. Perhaps the early creep feed offering could counteract the weight losses of the piglets caused by the enhanced activity in the GH system.

4.2. Behavioural testing In the series of tests to investigate the maternal behaviour, differences in maternal reactions could be obtained between GH and SH sows. These findings allow to conclude that housing conditions do influence maternal behaviour in sows. GH sows showed significantly stronger maternal reactions when they were tested in the HP, compared to SH sows when they were observed in the TA. However, all GH sows were usually housed in a SH system, an effect of the GH system on their maternal behaviour could already be observed in their first litter in the GH system. All sows were tested for their first time in the described maternal tests and, thus, it was for all sows a new situation. Additionally, the TA was used to create a test situation that was uncoupled from their housing environment. Nevertheless, the GH sows experienced the GH system for the first time, whereas, SH sows were usually housed in the SH system. A possibility to correct for that effect in further studies could be to use nulliparous sows which can then be observed over several lactations. However, this also increases the risk of habituation to the test procedure and the diversity of sows with different number of parities is lost. Furthermore, the experimenter was not blind to the treatment groups in the present study. However, a good structured and short ethogram was used with behaviours that were clearly defined to avoid misinterpretations.

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In the piglet scream test in the HP, GH sows were significantly more responsive to the piglet distress calls of their piglets than SH sows. In the study of Arey and Sancha (1996), sows housed in a family system showed also stronger postural reactions by standing up during a piglet scream test compared to SH sows. With regard to piglet crushing, the sensibility and responsiveness of the sows play a central role for piglet survival. For instance, Weary et al. (1996) showed that piglet survival increased immensely when the sow reacted to a trapped piglet within one minute. It was found that the screaming of a piglet is the most important stimulus for a sow to react (Hutson et al., 1991). Sows that showed a strong response to a screaming piglet were also calmer and showed fewer risky posture changes after birth (Thodberg et al., 2002). The positive correlation between high responsiveness and low piglet mortality caused by crushing are in accordance to the results of the present study. Although most piglet losses due to crushing occurred in the first days post partum, several behavioural studies conducted maternal tests later during lactation. For example Andersen et al. (2005) divided first two groups of sows into crushers and non-crushers regarding their piglet losses due to crushing. At day seven and eight post partum, these sows were tested in a piglet distress call test to investigate their maternal reaction. Also Held et al. (2006) performed the maternal tests at day five and six post partum regarding piglet losses which occurred in the first days post partum. Pitts et al. (2002) tested sows also seven days and one day before weaning concerning their maternal performances in several maternal tests. GH sows were highly responsive to the piglet distress calls in the test situation in the HP and crushed also significant lower piglets in the course of this study. A reason for the high responsiveness of GH sows could be that this is a necessity when housed in a GH system. In GH systems, different sows and piglets live together and, thus, it is important for sows to identify their natural piglets to allocate their maternal investment, whereas SH sows have no doubt that the piglets around them are their natural piglets. This could also explain the more frequent vocalisation of GH sows in the reunion test in the HP. A stronger and more constant communication between sows and their piglets were also observed in sows housed in ‘get-away’ and family systems compared to confined sows (Arey and Sancha, 1996; Pitts et al., 2002). SH sows remained near their screaming piglet more frequently and vocalised more compared to GH sows in the piglet scream test in the TA. Furthermore, they seemed to be more strained, by walking around during the separation test in the TA, whereas GH sows explored the TA more frequently. An explanation that SH sows were more active could be that they were not used to leave their home pen and move freely compared to GH sows. A reason that SH sows were more stressed compared to GH sows could be that SH sows were not used to separation from their piglets. However, GH sows were more experienced in being separated from their piglets as long as they could hear their piglets. In GH systems, it is common for sows and piglets not to be together the whole time. While the sow uses the running area, her piglets could rest in the pen for example. However, in the SH system the sows are used to always be surrounded by their piglets. Furthermore, it was observed in this study that the behavioural reactivity of the sows of the two housing systems changed in the course of time (between week 2 and 4). In all tests, the behavioural tension of the sows decreased. In week 4 the sows vocalised less frequently, were less active, had less contact with their piglets, nursed less frequently and explored the testing environment more often. A possible explanation could be that the sows became habituated to the test procedure. However, another reason for the decrease in behavioural tension and maternal care could be the beginning of the weaning process (Jensen et al., 1991; Bøe, 1993). Bøe (1993) observed a clear decline in the nursing frequency of sows and the time that sows spent with their piglets between the second and

fourth week of lactation. However, the behavioural tension in the piglet scream test in the HP increased between week 2 and 4 of testing. The piglet distress call seems to remain the most important stimulus for sows to react (Hutson et al., 1991). Regarding the management in the housing systems, GH sows had probably more contact to the stockperson than SH sows, especially because of the architecture of the GH system and the feeding procedure. However, there was no more interaction between feeder and sow regarding physical or verbal attention for the sows to minimize the differences between the two housing systems. Feeding is a positive association for pigs with a stockperson (Hemsworth et al., 1996). However, if an interaction between sows and stockperson during feeding would have an influence on the maternal performance in the tests, GH sows would react less tense in the piglet scream test in the home pen. In the present study, GH sows reacted significantly stronger in the piglet scream test in the home pen compared to SH sows. 5. Conclusion It could be concluded that housing conditions influence maternal behaviour in sows. In the present study, sows of both housing systems showed good maternal behaviour, depending on the tests carried out. GH sows showed good maternal behaviour in the HP and SH sows showed good maternal behaviour in the TA. However, GH sows had significantly fewer piglet losses. One explanation for the lower mortality rates in the GH systems could be that the stockpersons themselves were more familiar with the GH system. Furthermore, the possibility of free movement before farrowing could support more physical and psychological balance of GH sows, which could influence piglet mortality. Further research is needed to obtain more information, if the significantly lower piglet losses of GH sows are related to the stronger maternal reactions in the home pens of these sows and to the housing conditions ante partum. Conflict of interest None declared. Acknowledgment We gratefully acknowledge funding by Rentenbank. References Andersen, I.L., Berg, S., Bøe, K.E., 2005. Crushing of piglets by the mother sow (Sus scrofa)—purely accidental or a poor mother? Appl. Anim. Behav. Sci. 93, 229–243. Arey, D.S., Sancha, E.S., 1996. Behaviour and productivity of sows and piglets in a family system and in farrowing crates. Appl. Anim. Behav. Sci. 50, 135–145. Bøe, K., 1993. Maternal behaviour of lactating sows in a loosehousing system. Appl. Anim. Behav. Sci. 35, 327–338. Bohnenkamp, A.L., Traulsen, I., Meyer, C., Müller, K., Krieter, J., 2013. Group housing for lactating sows with electronically controlled crates: 1. Reproductive traits, body condition, and feed intake. J. Anim. Sci. 91, 3413–3419. Burri, M., Wechsler, B., Gygax, L., Weber, R., 2009. Influence of straw length, sow behaviour and room temperature on the incidence of dangerous situations for piglets in a loose farrowing system. Appl. Anim. Behav. Sci. 117, 181–189. Damm, B.I., Bildsøe, M., Gilbert, C., Ladewig, J., Vestergaard, K.S., 2002. The effects of confinement on periparturient behaviour and circulating prolactin, prostaglandin F2␣ and oxytocin in gilts with access to a variety of nest materials. Appl. Anim. Behav. Sci. 76, 135–156. Grandinson, K., Rydhmer, L., Strandberg, E., Thodberg, K., 2003. Genetic analysis of on-farm tests of maternal behaviour in sows. Livest. Prod. Sci. 83, 141–151. Held, S., Mason, G., Mendl, M., 2006. Maternal responsiveness of outdoor sows from first to fourth parities. Appl. Anim. Behav. Sci. 98, 216–233. Hellbrügge, B., Tölle, K.H., Bennewitz, J., Henze, C., Presuhn, U., Krieter, J., 2008. Genetic aspects regarding piglet losses and the maternal behaviour of sows. Part 1. Genetic analysis of piglet mortality and fertility traits in pigs. Animal. Hemsworth, P.H., Verge, J., Coleman, G.J., 1996. Conditioned approach-avoidance responses to humans: the ability of pigs to associate feeding and aversive

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