Effects of early contact between non-littermate piglets and of the complexity of farrowing conditions on social behaviour and weight gain

Effects of early contact between non-littermate piglets and of the complexity of farrowing conditions on social behaviour and weight gain

Applied Animal Behaviour Science 121 (2009) 16–24 Contents lists available at ScienceDirect Applied Animal Behaviour Science journal homepage: www.e...

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Applied Animal Behaviour Science 121 (2009) 16–24

Contents lists available at ScienceDirect

Applied Animal Behaviour Science journal homepage: www.elsevier.com/locate/applanim

Effects of early contact between non-littermate piglets and of the complexity of farrowing conditions on social behaviour and weight gain Tanja Kutzer, Beate Bu¨nger, Joergen B. Kjaer, Lars Schrader * Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Animal Welfare and Animal Husbandry, Do¨rnbergstrasse 25 & 27, 29223 Celle, Germany

A R T I C L E I N F O

A B S T R A C T

Article history: Accepted 11 August 2009 Available online 6 September 2009

In this study we tested if contact possibilities between non-littermate piglets and complexity of farrowing conditions affect the pre- and post-weaning behaviour, weight gain and skin lesions of piglets. Suckling sows were either kept in a group housing system (GH), in a single pen loose housing system (LH), or in conventional farrowing crates (FC). In the single pen systems a piglet door to the adjacent pen was opened on d 10 after farrowing in half of the pens so that piglets were able to enter the neighbouring pen (LH+ and FC+). For control, in the other half of single pens no piglet doors were opened (LH and FC). In the group housing system piglets also were allowed to freely move within the whole system on d 10 after farrowing. After weaning on d 28 piglets were kept in littered rearing pens in an open stable holding 20 piglets each. Piglets from contact pens were mixed with those they previously had contact to whereas piglets from control pens were mixed with unfamiliar litters. Data were obtained from 230 litters (113 sows with 1935 farrowed piglets). All piglets were scored for skin lesions immediately before and 4 days after opening the piglet doors, as well as immediately before and 4 days after moving into rearing pens. Behaviour (biting, fighting, drinking and laying) of piglets was recorded in the rearing pens in a 48-h period after weaning for 2  4 h. Treatments did not affect the level of skin lesions in the rearing period (H = 8.72, df 4, ns) nor daily weight gain until weaning (F4,216 = 1.21, ns). In the 48 h after moving to rearing pens, less intensive agonistic behaviour (fighting and biting) was observed in contact piglets (H = 53.36, df 4, P < 0.0001). Four days after weaning control piglets showed significantly higher numbers and more severe skin lesions than contact piglets and, in addition, lesion scores of piglets from the larger single farrowing pens with straw bedding were significantly lower compared to the single farrowing crate (H = 33.86, df 4, P < 0.0001). The latency for lying in the new rearing pen was decreasing (F4,93 = 25.76, P < 0.001) and the latency for drinking (F4,81 = 3.43, P = 0.01) was increasing with decreasing complexity and space allotment of the housing system but were not related to whether the piglets have had contact to other litters before weaning. Five weeks after weaning weight gain (F4,204 = 7.01, P < 0.0001) and BW (F4,207 = 5.34, P < 0.001) were higher in treatments offering contact. Our results show that familiarising piglets from different litters 10 day post partum by establishing contact possibilities through a piglet door reduces social stress at weaning and increases weight gain after weaning. Farrowing pens with straw bedding and enlarged space as offered in the farrowing pens and the group housing system can further decrease the level of harmful agonistic interactions after mixing unacquainted litters at weaning and can improve the adaptation of piglets towards the new environment of the rearing pen. ß 2009 Elsevier B.V. All rights reserved.

Keywords: Piglets Behaviour Weight gain Weaning Piglet barrier Co-mingling

* Corresponding author. Tel.: +49 5141 3846 0; fax: +49 5141 3846 117. E-mail address: [email protected]fli.bund.de (L. Schrader). 0168-1591/$ – see front matter ß 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.applanim.2009.08.004

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1. Introduction Weaning of piglets is one of the most critical phases in the whole pig production cycle. Factors causing stress at weaning include separation from the sow, transport, changing nutrition, different pathogenic pressures from a new environment, and increased aggression due to mixing of unfamiliar piglets (Held and Mendl, 2001; Jensen, 2002). Furthermore, weaning most often results in a period of low feed intake, poor weight gain or even weight loss and sporadically diarrhoea, and, thus, increasing risks for illness or even death of piglets (Blecha et al., 1985; Weary et al., 2008). Furthermore, BW at weaning and weight gain immediately after weaning can affect piglets’ growth until the end of fattening period (Pajor et al., 1991). Thus, not only with respect to animal welfare but also in order to optimize feed intake and growth, weaning stress should be reduced as much as possible. One of the most important stressors at weaning is aggressive fighting which occur during the formation of new social hierarchies when piglets from different litters are mixed, typically at an age of about 3–5 weeks in commercial production. Under semi-natural conditions piglets will leave the farrowing nest and co-mingle with unfamiliar littermates around day 10 post partum (Jensen and Redbo, 1987). At this age piglets from different litters are interacting with only little aggression (Petersen et al., 1989), fights are shorter and result in fewer injuries compared to older piglets (Pitts et al., 2000). Consequently, several studies have already been done about the possibility to co-mingle piglets of different litters before weaning either by opening a piglet door between adjacent pens (Pluske and Williams, 1996; Wattanakul et al., 1997; D’Eath, 2005; Hessel et al., 2006; Kanaan et al., 2008), by enabling contact in a communal piglet area (Weary et al., 1999; Weary et al., 2002; Parratt et al., 2006) or by group housing systems for lactating sows (De Jonge et al., 1996; Olsson et al., 1999; Cox and Cooper, 2001). These studies have shown that early social contact reduces aggression and injuries between piglets and that these differences in agonistic behaviour can persist in the fattening period (De Jonge et al., 1996; Olsson et al., 1999). Some studies also found at least a tendency for a better weight gain in contact piglets after weaning (Weary et al., 1999; Hessel et al., 2006) but others not (Wattanakul et al., 1997; Olsson et al., 1999; Parratt et al., 2006). Allowing contact between different litters during the suckling period does not only affect the social environment of piglets. In addition, the space which can be used by the piglets and the complexity of the physical environment is enlarged. Comparing piglets which were raised in single farrowing systems differing in enrichment and space allotment, Chaloupkova´ et al. (2007a) did not find differences in agonistic behaviour when piglets were mixed at weaning, but at the age of 3 and 6 months pigs farrowed in the enriched pens showed less aggressive behaviour in a food competition test. Also when pigs are kept in an enriched environment for their whole lifespan they seem to be less aggressive compared to pigs kept in barren environment (Beattie et al., 2000; de Jong et al., 2000).

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There is evidence that farrowing condition can also influence the behavioural reactivity towards non-social challenges. Piglets raised in enriched and larger farrowing pens showed less behavioural signs of distress (e.g. vocalisations, locomotion) in a human encounter test performed 3 days before weaning compared to piglets kept in barren farrowing crates (Chaloupkova´ et al., 2007b). Beattie et al. (2000) raised piglets either in farrowing crates or in farrowing pens bedded with straw and kept the pigs in barren or enriched pens also after weaning. When subjects were tested 14 weeks after weaning in a novel object test pigs from enriched pens reacted less fearful (e.g. shorter latency to contact object, more locomotion) compared to pigs from barren pens. Hillmann et al. (2003) raised piglets either in single farrowing pens or in a group farrowing system. Piglets from the single pens showed more behavioural signs of distress (e.g. locomotion, vocalisation) in a novel environment test which was done 2–3 days before and after weaning compared to the piglets from the group farrowing system. Jansen et al. (2009) tested whether barren and enriched farrowing condition affects spatial learning in pigs and found that piglets from enriched housings showed a different explorative pattern compared to pigs from a barren housing. The opportunity to explore a more complex environment during farrowing may thus enable piglets developing better coping strategies to non-social challenges such as an unknown pen. The effects of early contact between non-littermates during the suckling period and of non-social enrichment on the piglets’ behaviour and performance at weaning have, until now, not been tested in parallel. In this study we kept piglets in barren pens with farrowing crates and in larger farrowing pens equipped with straw bedding. Half of both housings were equipped with piglet doors to enable contact between piglets of different litters from d 10 post partum. In addition, piglets were kept in a group housing system as a positive control. We hypothesised that litters which were co-mingled during suckling period will show less agonistic interactions at mixing after weaning. Due to effects of enrichment piglets kept in the larger single pens with straw bedding were expected to show less agonistic interactions after weaning compared to the litters from the barren single pens with farrowing crates. In addition, we expected that with an increasing environmental complexity of farrowing pens the piglets would cope better with the new environment after weaning. The effect of both the social and the non-social enrichment were also expected to be indicated by a better weight gain. 2. Materials and methods 2.1. Housing Sows and piglets were kept in three farrowing rooms with eight pens each at the experimental station of the Federal Research Institute for Animal Health in Mariensee. The farrowing room with conventional crates was forced ventilated and heated; the rooms with the loose housing single pens and the group housing were not temperaturecontrolled. Within each farrowing room there were four

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farrowing pens on each side of a central feeding passage. The farrowing crates were equipped with partly slatted floors whereas the loose housing single pens and the group housing room had concrete floors. Within the group housing rooms there were eight farrowing pens. The pens of all housing systems were separated by solid partitions and had an infrared-heated piglet resting area. Sows were moved into the farrowing rooms according to the all in/all out principle approximately 1 week ante partum. On d 10 after farrowing, the piglet doors (30 cm  40 cm) between two adjacent single farrowing pens on both sides of the feeding passage were opened, but sows remained confined in their crates or pens, respectively. In the other four pens of both single farrowing systems sows and litters remained confined in their pens (control groups). In the group housing system piglet barriers, confining piglets (but not the sows) in their respective part of the group housing pen during parturition, were removed on d 10. Thus, from d 10 also the piglets could move freely in the whole group housing pen and can co-mingle with seven other litters and sows. For a detailed description and name convention of the pens see Table 1. At weaning d 28 post partum the sows were removed from farrowing pens and the piglets stayed there for four days. Then the piglets were moved into nursing pens in a separate stable with outdoor climate. Each of the 10 pens in this stable was sized for 20 piglets (2.0 m  6.0 m) and split into an activity area (5.9 m2) and a covered resting area (4.0 m2), both solid-floored with straw-bedding. Water was offered with two nipple drinkers in a small slatted area (2.1 m2) in front of the pen. Feed troughs were placed in the resting area with an animal-feeding place ratio of 2:1. On average 18.4 (0.25 S.E.) piglets were placed per pen. Litters from the respective housing system which had contact during suckling period remained together in the nursing pens. 2.2. Animals In total, 113 sows (German Large White  German Landrace) at different ages were used in this study. They were kept in a stable with solid concrete floor and additional straw bedded lying areas until 1 week prior to expected parturition. Most sows (94%) were artificially inseminated with Pie´train sperm whereas a few sows (6%) were serviced by a German Landrace boar, but these were evenly distributed across treatments. No pharmaceutical induction was used. In total, data were obtained from 230 litters (75 GH, 40 FC, 40 FC+, 42 LH and 33 LH+) and

1935 piglets, respectively. Sows were randomly assigned to the three treatments according to the standard production process at the experimental station. In the rare cases of very large litter sizes (more than 14 living piglets per litter which occurred three times) or agalaxy some of the piglets were cross fostered to obtain balanced litter sizes. In the first week post partum, all piglets were handled following standard commercial practices (tail docking, earmarking, supply with iron, castration of males). 2.3. Feeding As an additional feed source the same solid feed was offered from the first week post partum until 5 weeks after weaning to the piglets ad libitum in a dry feeder. Water was offered ad libitum by nipple drinkers throughout the whole trial period. Sows were fed with dry standard lactation feed (14 MJ ME/kg) ad libitum during lactation in a feeder to which the piglets did not have access. Due to wasting of feed from the trough it was not possible to record the feed consumption of piglets and sows reliably. Sows in the loose housing and group housing systems got additional hay and straw at racks daily. 2.4. Data collection 2.4.1. Reproductive parameters of the sows For each sow, the following data were recorded: number of gestation, number of piglets born alive, number of piglets born dead, number of piglets crushed, number of other losses and number of weaned piglets. 2.4.2. Behaviour In the farrowing pens the frequency of crossing the doors by individual piglets was continuously recorded by a transponder–antenna-system. These recordings were done for 48 h on day 1–2, on day 7–8, and on day 14–15 after opening the doors. The transponder–antenna-system based on commercial ear tags (HDX Transponder LW, Allflex, Hamburg, Germany) was built to match the specific design of the doors. Validation by video recording showed that about 75% of the crossings were recognized by the system. Thus, the amounts of passages per piglet were underestimated but unbiased. The reason for this underestimation was that the transponders could not be read whenever a piglet rested directly in front of one of the antennas.

Table 1 Definition of experimental groups and pen dimensions. Group

Description

Dimensions

FC

Conventional farrowing crate without contact between piglets; partly slatted floor; no straw Farrowing crate with piglet door, opened 10 days post partum; partly slatted floor; no straw Modified conventional FAT2 pen (loose-housing system with nest and dunging area) without contact between piglets; concrete floor; straw provided Modified FAT2 pen (loose-housing system with nest and dunging area) with piglet door, opened 10 days post partum; concrete floor; straw provided Group housing system for eight lactating sows and their litters; concrete floor; straw provided

Pen 2.00 m  2.25 m, crate 0.65 m  1.90 m

FC+ LH LH+ GH

Pen 2.00 m  2.25 m, crate 0.65 m  1.90 m 2.40 m  3.00 m 2.40 m  3.00 m Whole room: 11.10 m  10.10 m, farrowing boxes 1.85 m  2.50 m  1.40 m

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During the 4 h immediately after moving the piglets from the farrowing pens to the nursery, the behaviours fighting, biting, lying and drinking were recorded by direct observation and recordings were repeated 24 h later except of drinking and lying. Fighting behaviour was defined as mouth-to-head or mouth-to-body attacks with strong thrusts sideways and upwards. This behaviour normally lasts between a few seconds up to several minutes. Biting behaviour was defined as grasping and applying pressure to other piglets with the teeth to hold, puncture, or shear it without showing fighting behaviour. Biting behaviour often occurs after social hierarchy fights for testifying dominance and only lasts some seconds. In order to allow an individual recording of behaviour, all piglets were individually marked on the back with commercial colour marking pens before moving to rearing pens. Recordings were done by a group of five trained observers. Fighting and biting were noted as events. Latency to drink was recorded for each piglet individually, latency to lie down was recorded for group, i.e. the criterion was reached when all pigs in a pen were lying down. Maximum latency was set to 4 h, so piglets without an observation of drinking, respectively, groups not lying were set to 4 h latency. 2.4.3. Scoring of skin lesions The integument of piglets was scored for skin lesions four times: immediately before (scoring 0) and 4 days after removal (scoring 1) of the doors between the pens, on the day moving to rearing pens (scoring 2) and finally another 4 days after moving to the rearing stable (scoring 3). The integument was scored at three parts of the body: head and ears, shoulder and flank, and hindquarters. Each part was scored from ‘‘0’’, ‘‘1’’ or ‘‘2’’. Score ‘‘0’’ was given if no lesion could be detected at the respective body part, score ‘‘1’’ if at least one but less than 10 superficial skin lesions were found, and score ‘‘2’’ if more than 10 superficial skin lesions or if one or more deep lesion (skin broken and evidence of haemorrhage) were visible. Scoring was performed by two trained observers. 2.4.4. Body weight Each piglet was weighed individually on d 0 (birth), 7, 14, 21, 28 (weaning), 32 (moving into nursery after farrowing) and on d 46 and 67. Weightings on d 0 to d 21 were done exactly on these days; the other weightings were done at 3 days of age. 2.5. Statistical analysis For all statistical analysis we used the SAS statistical analysis system version 9.1 (SAS Institute Inc., NC, USA). The reproductive parameters of the sows were related to the systems FC, LH and GH, regardless whether there was a piglet door or not, because the majority of all piglet losses happened before opening the piglet doors at day 10. Number of piglets born alive, number of piglets born dead, number of piglets crushed, number of other losses and number of weaned piglets were analysed using Kruskal– Wallis (KW) tests (procedure npar1way) with litters as statistical units.

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Body weight and gain was recorded and analysed using individual pigs as statistical units using a repeated measures analysis of variance (procedure mixed) with housing system, season and gender of piglets as fixed factors and litter within sow as repeated measure and using Tukey–Kramer correction of P-values in the post hoc tests. The effect of doors was tested using only crates and loose housing with or without doors, the final model including door and housing system. Traits related to the litters were analyzed using each litter as a statistical unit during farrowing (number of crushed piglets, number of other piglet losses and number of weaned piglets) and each nursery pen (cohort of 2 or 3 litters) during the rearing period (lesions, fighting, drinking, lying). The frequency of passing the piglet doors was expressed by the mean total number of crossings per piglet during the 3  48 h of recordings. Data were analysed with repeated measures analysis of variance (proc mixed) with housing system and season as fixed factors and litters within sow as repeated measures. Based on the lesion scores obtained from the different body parts we calculated a total lesion score ratio for each observation phase as follows: total lesion score ratio ¼ ðscore head and ears þ score shoulder and flank þ score hindquartersÞ total possible score This process converted data from an ordinal scale to a ratio scale allowing analysis with parametric statistics. Lesion score ratios could not be transformed into a normal distribution, however, and were analysed using the Kruskal–Wallis test (procedure npar1way) and, for pair wise comparisons, the Wilcoxon signed-rank test. Fighting and biting were expressed as the observed number of events per pen divided by the number of piglets per pen showing the particular behaviour. Fighting and biting could not be transformed to normal distributions and were analysed using the Kruskal–Wallis test (npar1way) and Wilcoxon signed-rank test for pair wise comparisons. Drinking and lying were expressed by the mean latency to drink, respectively, lie down for the group (rearing pen) and subjected to analysis of variance. For all analyses, significance was considered to be P < 0.05. 3. Results 3.1. Reproductive parameters Throughout the whole observation period the proportion of primiparous sows amounted to 16%. Forty-six percent of the sows contributed only one litter to the data, 26% had two parturitions, 10% had three parturitions, 12% contributed four and 5% of the sows contributed 5 litters to the data. The average number of gestations was balanced over systems. Mean birth weight per piglet averaged 1.58 kg (0.01 S.E.) over all systems and gestation numbers with no significant differences between treatments (KW test, Z(2) = 7.51, ns). The litter size averaged 10.30 (0.15) total

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born piglets and was not influenced by housing system. Also, neither the number of dead born piglets (0.43  0.05 S.E.; KW test, Z(2) = 0.68, ns) nor the number of weaned piglets (8.44  0.14; KW test, Z(2) = 0.76, ns) per litter differed between treatments. However, the number of dead piglets due to crushing and due to other reasons significantly differed between housing systems (KW test, Z(2) = 7.71, P < 0.05): sows in the group housing system crushed significant more piglets during the first 10 days (1.13  0.16) than sows from loose housing pens (0.93  0.14) and farrowing crates (0.59  0.09). On the other hand, sows in the farrowing crates showed significantly (KW test, Z(2) = 9.76, P < 0.01) higher other piglet losses (especially runts, piglets culled due to diarrhoea and other diseases, and piglets with spread legs, 0.90  0.14 S.E.) than sows from loose housing pens (0.36  0.07) and group housing system (0.45  0.09). 3.2. Use of piglet doors In both farrowing systems with a door (FC+ and LH+) the piglets used it very intensively. Piglets from FC+ crossed the piglet door in the 3  48 h observation period significantly more often than piglets in system LH+ (373 vs. 323 times, ANOVA, F41,1 = 5.75, P < 0.05), i.e. 62 vs. 54 times per 24 h, despite a high variation between individual piglets ranging from 60 to 1167 (10 to 195 per 24 h) passages per piglet in FC+ and 23 to 866 (4 to 144 per 24 h) passages per piglet in LH+. 3.3. Agonistic behaviour Housing system significantly affected the intensity of fighting after moving to the nursery (KW test, Z(4) = 67.27, P < 0.001). Pair wise comparisons revealed that fighting was more intensive in FC compared to FC+ (2.18 relative fights vs. 0.36 relative fights, Wilcoxon, Z = 4.86, P < 0.001) and in LH compared to LH+ (1.73 vs. 0.26, Wilcoxon, Z = 4.87, P < 0.001). Fighting in the two pens differing in complexity and space allotment (FC vs. LH, FC+ vs. LH+) did not differ significantly (see Fig. 1 for further details). The treatments significantly affected the intensity of biting (KW test, Z(4) = 53.36, P < 0.001). Biting was significantly less intensive in GH, FC+ and LH+ piglets

Fig. 1. Number of observed fightings divided per fighting piglets (mean  SD) in rearing pen during 2  4 h observation period. For each housing system, means followed by different letters differ significantly (P < 0.05, Wilcoxon signed-rank test).

Fig. 2. Number of observed bites divided per biting piglets (mean  SD) in rearing pen during 2  4 h observation period. For each housing system, means followed by different letters differ significantly (P < 0.05, Wilcoxon signed-rank test).

compared to the controls without contact during the suckling period (FC) (0.63  0.08 bites resp. 0.73  0.11 resp. 0.78  0.14 vs. 2.93  0.36 (Wilcoxon, P < 0.001) or vs. LH (2.05  0.23), (Wilcoxon, P < 0.001)) and did not differ between GH, FC+ and LH+ treatments (Wilcoxon, Z = 0.11, ns) (Fig. 2). 3.4. Lesion scores No skin lesions were found at the scoring immediately before opening doors between pens (scoring 0). Four days after opening the piglet doors (scoring 1) we found lesions at ear and shoulders of a few piglets, but there was no significant effect of the housing system on lesion scores (KW test, Z(4) = 8.72, ns). At scoring 2, done immediately before grouping on the day at which the piglets were moved to the nursery, treatment significantly affected total lesion score ratio (KW test, Z(4) = 33.86, P < 0.001). In detail, we found some skin lesions on the body parts head and ear and on shoulder and flank, but not at the hindquarters. We did not find any deep or severe skin lesions and, thus, all lesions were scored for a ‘‘1’’ at maximum. The total lesion score ratio varied between GH and all other systems except LH+ (Mann–Whitney-U, FC vs. GH: P < 0.001, FC+ vs. GH: P < 0.001, LH vs. GH: P < 0.001). For detailed data see Table 2. Four days after moving to nursery we found that comingled piglets had a significantly lower total lesion score ratio than piglets from control systems without doors (KW test, Z(4) = 75.25, P < 0.001). Pair wise comparisons revealed that skin lesions were more severe in FC compared to FC+ (0.17  0.03 relative skin lesion score vs. 0.03  0.01, Wilcoxon, Z = 5.77, P < 0.001) and in LH compared to LH+ (0.09  0.02 vs. 0.02  0.01, Wilcoxon, Z = 3.64, P < 0.001) (Table 2). Also the control systems differed significantly (FC vs. LH: Z = 2.67, P < 0.01). We did not find any differences between the systems with contact possibilities between litters. Piglets from single loose housing pens without contact to the neighbouring litter tended to show less lesions compared to the respective piglets from farrowing crates (Table 2). While only between 3.4% (GH), 3.3% (LH+) and 2.6% (FC+) of piglets in the housing systems with contact between litters showed any skin lesions on shoulder and flank (maximum

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Table 2 Relative skin lesion score (mean score  standard deviation) in relation to housing system. Housing system

Lesion score the day before moving to nursery Lesion score 4 days after moving to nursery

FC

FC+

LH

LH+

GH

0.0099 (0.0357)c

0.0298 (0.0751)b

0.0155 (0.0255)b

0.0308 (0.0445)ab

0.0458 (0.0572)a

0.1691 (0.1217)a

0.0205 (0.0338)b

0.1107 (0.0916)c

0.0198 (0.0363)b

0.0162 (0.0231)b

For each housing system, means followed by different letters differ significantly (P < 0.05, Wilcoxon signed-rank test).

score ‘‘1’’), piglets in control systems showed much more skin lesions at these body parts (FC: 41.6%, LH: 27.1%) and with maximum values of ‘‘2’’ these lesions were more severe. 3.5. Drinking The mean latency for drinking over all systems was 1:04 h (1:00 STD). 14.2% of all piglets did not drink within the observation period. We found significant differences between treatments (ANOVA, F4,81 = 3.43, P = 0.01) and these differences refer predominantly to the farrowing housing systems and not to the existence of a piglet door. Piglets from GH showed a significant higher latency for drinking than piglets from FC (P = 0.01). Systems LH+, LH and FC+ did not differ significantly from any other housing system (see also Fig. 3). Latency to drink was significantly affected by season (ANOVA, F3,81 = 7.58, P < 0.001). The latency in autumn (1:32 h  1:16 STD) and winter (1:31 h  0:52 STD) was higher compared to the latencies in spring (0:40 h  0:35 STD) and summer (0:45 h  0:45 STD; spring vs. summer: ns, spring vs. autumn: P < 0.01, spring vs. winter: P < 0.01, summer vs. autumn: P < 0.05, summer vs. winter: P < 0.01, autumn vs. winter: ns).

the possibility of contact between litters. Piglets from GH showed the lowest latency for lying (0:35 h  0:23) and differed significantly from all other piglets (GH vs. FC: P < 0.001, GH vs. FC+: P < 0.001, GH vs. LH: P < 0.001, GH vs. LH+: P < 0.05). Piglets from both loose housing systems showed a significant higher latency than piglets from GH (LH: 1:33 h  0:42 STD, LH+: 1:13 h  0:32 STD, LH vs. LH+, P = ns), but a significant lower latency than piglets from FC (2:29 h  1:05 STD) (LH vs. FC: P < 0.01, LH+ vs. FC: P < 0.001). Latencies of piglets from FC+ (2:05 h  0:47 STD) did not differ significantly from systems FC and LH but from LH+ (P < 0.01) and GH (see also Fig. 4). In general, latencies increased with decreasing complexity and space allotment of the housing system, i.e. for piglets growing up in group housing over loose housing to farrowing crates. 3.7. Body weight and gain

The mean latency for all systems was 1:26 h (0:57 STD). Two rearing pens, corresponding to 2% of all observations, did not reach the criterion ‘all piglets lying down’ within the 4 h observation period. We found significant differences between housing treatments (ANOVA, F4,93 = 25.76, P < 0.001), but differences were not related to

The average daily weight gain (STD) from day 0 to 28 was 248 g (52) and was not affected by housing system (ANOVA, F4,216 = 1.21, ns, Table 3). In the four days after weaning, piglets in LH+ and LH systems showed the highest weight gain, but LH piglets did not differ significantly from GH piglets. Piglets in the farrowing crates had a significantly lower body weight gain over these 4 days. Housing system affected bodyweight at d 46 (ANOVA, F4,203 = 4.22, P = 0.003) with lowest weight in pigs from the farrowing crates (Table 3). Piglets from housing system GH had a significant higher body weight than piglets from systems FC and FC+, but did not differ significantly from housing systems LH and LH+. Piglets from system FC+ had the lowest body weight, but did only differ signifi-

Fig. 3. Latency of first drinking per piglet (mean  SD) immediately after moving to nursery. For each housing system, means followed by different letters differ significantly (P < 0.05).

Fig. 4. Latency until first lying of all piglets (mean  SD) in rearing pen immediately after moving to nursery. For each housing system, means followed by different letters differ significantly (P < 0.05).

3.6. Lying

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Table 3 Weight gain and absolute bodyweight (kg  standard deviation) of piglets in different housing systems (n: number of litters, lsw: mean litter size at weaning). FC (n = 40) (lsw = 7.98) Daily weight gain until d 28 Weight gain between weaning and moving to nursery (duration 4 d) Bodyweight at d 46 Bodyweight at d 67 Weight gain in 5 weeks of rearing in nursery

FC+ (n = 40) (lsw = 8.70)

0.25 (0.06) 0.25 (0.42)c

0.25 (0.05) 0.30 (0.41)c

11.56 (2.38)bc 21.04 (4.64)c 12.48 (3.72)c

11.40 (2.41)c 21.86 (4.74)cb 13.48 (3.70)bc

LH (n = 42) (lsw = 8.02) 0.26 (0.05) 0.64 (0.45)ab 12.54 (2.45)ab 22.93 (4.45)ac 13.82 (3.49)ac

LH+ (n = 34) (lsw = 9.36) 0.25 (0.05) 0.69 (0.42)a 12.23 (2.35)abc 23.58 (3.96)ab 14.78 (2.90)bc

GH (n = 74) (lsw = 8.38) 0.25 (0.05) 0.59 (0.46)b 12.60 (2.41)a 23.83 (4.60)a 14.93 (3.75)a

For each housing system, means followed by different letters differ significantly (P < 0.05).

cantly from LH and GH piglets. Also housing season had an influence on body weight (ANOVA, F3,204 = 4.84, P < 0.01) with lower BW in summer (11.57 kg) compared to spring (12.48 kg, P < 0.01), autumn (12.32 kg, P < 0.05) and winter (12.73 kg, P < 0.001). Bodyweight at d 67 showed a similar picture: we found significant effects of the housing system (ANOVA, F4,207 = 5.34, P < 0.001), but not of season, see Table 3. Weight gain per piglet during the 5 weeks postweaning was significantly affected by housing system (ANOVA, F4,204 = 7.01, P < 0.001) and season (ANOVA, F3,205 = 3.27, P < 0.05). Piglets from GH gained significantly more weight than piglets from FC and FC+. FC piglets had also significant lower weight gain than piglets from LH+ (Table 3). When comparing housing system with and without contact possibilities the piglets from systems with a door gained significantly more (14.2 vs. 13.4 kg, ANOVA, F1,130 = 4.15, P < 0.05). 4. Discussion Piglets kept in farrowing crates as well as in single loose housing pens frequently used a door which enabled contact to piglets from another litter in an adjacent pen. When the piglets were moved to rearing pens after weaning they show less intensive agonistic behaviour and less skin lesions. In addition, skin lesions and performance were affected by the space allotment and enrichment of housing conditions during suckling period. Weight gain and body weight were highest in piglets from the group housing system and lowest in piglets from farrowing crates and were affected by both social and nonsocial conditions during the suckling period. From the first day after opening the door between two adjacent pens at day 10 post partum the piglets contacted the other litter very frequently. The use of piglet doors remained attractive for the whole farrowing period as also observed by Weary et al. (1999) testing a communal piglet area for up to 3 litters. Interestingly, piglets from farrowing crates used the door more often than piglets from single loose housing pens. The additional space in the adjacent pen might have been more attractive to the piglets in the pens with farrowing crates because these offered less space (4.5 m2) than the loose housing pens (7.2 m2). During the farrowing period and after opening the doors at day 10 post partum we found only very few skin lesions with no differences between treatments. This corresponds to the results of other investigations (Weary et al., 1999; Cox and Cooper, 2001; Weary et al., 2002),

however, some studies even found an increase in fighting between piglets after enabling contact between litters (Wattanakul et al., 1997; D’Eath, 2005; Parratt et al., 2006; Kanaan et al., 2008). In our study we only found significantly more lesions in co-mingled piglets at the last day in the farrowing pens, i.e. the day before grouping. These lesions were less severe and only a small proportion of piglets were affected. The differences between studies concerning these effects may result from different size and equipment of pens allowing piglets to hide to a different extent. For example, in the study of Parratt et al. (2006) the piglets showed a significant increase in fighting after mixing only in the additional piglet area behind the pens but not in the crates. In the 48 h period directly after regrouping in the rearing pen the piglets from single farrowing pens with no contact to other litters showed significant higher lesion scores compared to piglets grouped with piglets they already knew from the farrowing pens. The differences in lesions obviously resulted from differences in severity of agonistic behaviour after regrouping. The piglets from farrowing pens with contact showed less intensive fighting and biting compared to the piglets from farrowing pens without contact. In addition, lesion scores of piglets from the larger single loose-house farrowing pens with straw bedding were significantly lower compared to the single farrowing crate. This shows that enrichment during the suckling period decrease the level of harmful agonistic interactions after mixing unacquainted litters at weaning. The differences in lesions scores between the housing systems without contact between litters were higher than the differences between the housing systems with contact between litters. This indicates a stronger effect of the social contact before weaning on the agonistic behaviour after weaning compared to the effect of environmental enrichment on agonistic behaviour. The latencies for lying and drinking in the first 4 h after rearing were not affected by whether the piglets had contact to other litters or not during farrowing. Instead, the latency for lying was decreasing and the latency for drinking was increasing with decreasing complexity and space allotment of the housing system, i.e. for piglets growing up in group housing over loose housing to farrowing crates. This indicates that non-social enrichment of farrowing systems such as straw bedding and additional space leads to a faster adaptation and a lower stress response of piglets towards the new environment (Beattie et al., 2000; Hillmann et al., 2003; Chaloupkova´ et al., 2007b) or to less explorative behaviour in these piglets

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(Jansen et al., 2009). Another explanation would be that piglets involved in agonistic interactions needed more time for lying down and had a higher demand for water due to exhaustion. However, this would have resulted in a higher latency for lying and a lower latency for drinking in the piglets from farrowing housings without contact to other piglets. We also found that in spring and summer the piglets started earlier with drinking after moving into rearing pens. This is likely to be related to the higher ambient temperatures during these seasons and the resulting higher demand for water. Before rearing BW and gain were not affected by housing system. During the four days between weaning and moving to the rearing pen, however, piglets from the farrowing crates showed the lowest weight gain compared to the piglets from the other treatments. At day 46 and day 67 piglets from the group housing system had a higher body weight compared to piglets from the systems with farrowing crates. In addition, there was a tendency for higher body weight and gain in the piglets from the loose housing systems compared to the piglets from the respective farrowing crates. This indicates a combined effect of both the social and the non-social enrichment on weight performance of piglets which is likely to result from a reduced stress response towards mixing and the new environment of the rearing pen. Whereas some other studies also found at least a tendency for a better weight gain in contact piglets after weaning (Weary et al., 1999; Hessel et al., 2006) others did not (Wattanakul et al., 1997; Olsson et al., 1999; Parratt et al., 2006). Due to the high variability of weight gain and the comparable low effect of farrowing housing condition on weight performance after weaning a high number of litters has to be included in order to detect significant differences. Using a total of 230 litters this was possible in the present study. Beside housing conditions also the season affected the body weight. In summer piglets showed the lowest body weight compared to the other seasons which is likely to have resulted from a lower feed intake due to high ambient temperatures (Rinaldo and Le Dividich, 1991). However, it was not possible in our study to record the feed intake of piglets because uncertain amounts of food were wasted by the piglets. The number of piglets born did not differ between housing systems. However, the piglet losses due to crushing were higher in the group housing systems whereas sows in the farrowing crates showed significant higher other piglet losses than sows from loose housing pens and group housing system. In the end, the number of weaned piglets did not differ between housing systems confirming the results of other studies on different farrowing systems (Cronin et al., 1998; Weber et al., 2007). Although not explicitly recorded in this study, we never observed cross-suckling in the contact pens or in the group housing system during the daily control. If cross-suckling had occurred we would have expected less weight gain in the contact pens or the group housing system compared to the single pens. The risk of cross-suckling could have been higher in the group housing system as sows in the single housing systems with contact remained in their pens

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making it easier for the piglets to find their mother (Wattanakul et al., 1997). Furthermore, sows in the single farrowing pens comparable with group housing sows let their milk down quite synchronized decreasing the risk of cross-suckling (Sˇilerova´ et al., 2006). Our results show that piglets to a great extend used doors between two adjacent pens to mingle with pigs from another litter. This contact between different litters had very positive effects on behaviour and performance after weaning primarily by decreasing the intensity of aggressive interactions after moving to the rearing pens. Enlarged space and straw bedding as offered in the farrowing pens and the group housing system additionally reduced the number of lesions at mixing after weaning and improved the adaptation of piglets towards the new environment of the rearing pen. As a consequence, stress during weaning and lesions due to agonistic interactions could be reduced and this was accompanied by positive effects on piglets’ performance. The integration of piglet doors in common farrowing pens had only minor economic costs and, very important from an economic perspective, no additional space was needed in the stable. In order to meet the requirements of modern production requesting larger groups of weaners, additional research is required to examine if co-mingling 4 litters or more during the farrowing period will have the same positive results on welfare and production parameters. Acknowledgment The authors would like to thank the team of technical assistants for their skilled work, Oliver Sanders, who modified the transponder–antenna-system, and the farm staff for animal care. References Beattie, V.E., O’Connell, N.E., Moss, B.W., 2000. Influence of environmental enrichment on the behaviour, performance and meat quality of domestic pigs. Livestock Production Science 65, 71–79. Blecha, F., Pollmann, S., Nichols, D.A., 1985. Immunologic reactions of pigs regrouped at or near weaning. American Journal of Veterinary Research 49, 1934–1937. Chaloupkova´, H., Illmann, G., Bartosˇ, L., Sˇpinka, M., 2007a. The effect of pre-weaning housing on the play and agonistic behaviour of domestic pigs. Applied Animal Behaviour Science 103, 25–34. Chaloupkova´, H., Illmann, G., Neuhauserova´, K., Toma´nek, M., Valis, L., 2007b. Preweaning housing effects on behavior and physiological measures in pigs during the suckling and fattening periods. Journal of Animal Science 85, 1741–1749. Cox, L.N., Cooper, J.J., 2001. Observations on the pre- and post-weaning behaviour of piglets reared in commercial indoor and outdoor environments. Animal Science 72, 75–86. Cronin, G.M., Dunsmore, B., Leeson, E., 1998. The effects of farrowing nest size and width on sow and piglet behaviour and piglet survival. Applied Animal Behaviour Science 60, 331–345. D’Eath, R.B., 2005. Socialising piglets before weaning improves social hierarchy formation when pigs are co-mingled post-weaning. Applied Animal Behaviour Science 93, 199–211. de Jong, I.C., Prelle, I.T., van de Burgwal, J.A., Lambooij, E., Korte, S.M., Blokhuis, H.J., Koolhaas, J.M., 2000. Effects of rearing conditions on behavioural and physiological responses of pigs to preslaughter handling and mixing at transport. Canadian Journal of animal science 80, 451–458. De Jonge, F.H., Bokkers, E.A.M., Schouten, W.G.P., Helmond, F.A., 1996. Rearing piglets in a poor environment: developmental aspects of social stress in pigs. Physiology and Behavior 60, 389–396.

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