Newcastle upon Tyne NE1 7RU, United Kingdom b Meat & Livestock Commission, Winterhill House, Milton Keynes MK6 1AX, United Kingdom

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1 Applied Animal Behaviour Science 99 (2006) Influence of different types of environmental enrichment on the behaviour of finishing pigs in two different housing systems 1. Hanging toy versus rootable substrate Kamara Scott a, *, Lisa Taylor b, Bhupinder P. Gill b, Sandra A. Edwards a a School of Agriculture, Food and Rural Development, University of Newcastle, Newcastle upon Tyne NE1 7RU, United Kingdom b Meat & Livestock Commission, Winterhill House, Milton Keynes MK6 1AX, United Kingdom Accepted 28 October 2005 Available online 2 December 2005 Abstract This study aimed to assess the effects of environmental enrichment with either hanging manipulable toys or rootable substrates on the behaviour of finishing pigs in two contrasting housing systems. Thousand one hundred and twenty-four (Large White Landrace) Large White pigs were housed contemporarily in either a straw-based (ST) or fully slatted (FS) building from 35 kg to slaughter at 104 kg liveweight. In each building, half the pens received additional enrichment in the form of a hanging plastic toy (Bite-Rite). In the ST house the remaining pens were enriched only by the straw bedding. The remaining pens in the FS house were provided with hoppers containing shreds of unmolassed sugar beet pulp. The level of Bite-Rite manipulation was significantly higher in the FS system than in the ST system (P < 0.05). Within the FS system, the sugar beet pulp occupied the pigs for more time than the Bite-Rite object (P < 0.05). Neither object provided a level of occupation close to that of straw bedding in the ST system. In the absence of straw, more investigatory behaviours were directed towards pen components (P < 0.001), however, no significant differences in * Corresponding author. Tel.: ; fax: address: Kamara.Scott@newcastle.ac.uk (K. Scott) /$ see front matter # 2005 Elsevier B.V. All rights reserved. doi: /j.applanim

2 K. Scott et al. / Applied Animal Behaviour Science 99 (2006) pig-directed behaviours were observed. Further study is required to identify functional forms of environmental enrichment for pigs in unbedded systems. # 2005 Elsevier B.V. All rights reserved. Keywords: Environmental enrichment; Pigs; Straw; Fully slatted; Behaviour 1. Introduction Studies have suggested that environmental enrichment can improve the welfare of growing pigs through the provision of substrates for exploratory and manipulatory behaviour (Beattie et al., 2000; Petersen et al., 1995; Arey, 1993). EU Directive 2001/93/ EU states that pigs must have permanent access to materials such as straw, hay, wood, sawdust, mushroom compost and peat to enable proper investigation and manipulation. This extends the previous Directive 91/630/EEC which stated that:...all pigs...shall have access to straw or other material or object suitable to satisfy those [behavioural] needs. However, the suitability of different forms of enrichment is still the subject of debate. Straw can offer advantages for animal welfare due to its use as a recreational stimulus, a nutritional substrate and as bedding (Fraser et al., 1991). In barren rearing environments, the highly motivated oral activities of rooting and chewing tend to become re-directed towardspenmates(e.g.lyons et al., 1995; Kelly et al., 2000) and pen hardware (e.g. Lyons et al., 1995; Guy et al., 2002). Despite this, a recent review of housing systems in current use within the EU shows that the majority of finishing pigs are kept in buildings with slatted floors (Hendriks et al., 1998), with no access to straw for either bedding or occupation. The use of rooting materials, such as straw, in slatted systems can cause difficulties for slurry management and it is therefore important to establish whether alternative forms of environmental enrichment, such as hanging objects, can be equally effective. The aim of this study was to assess the effects of environmental enrichment with either hanging manipulable toys or rootable substrates on the behaviour of finishing pigs in two contrasting housing systems. 2. Materials and methods 2.1. Experimental design Two different environmental enrichment treatments were compared in each of two housing systems, giving a total of four treatments each replicated across eight pens of pigs. In a straw-based building, pens with straw bedding as the only form of enrichment were compared with pens which had an additional hanging plastic toy. In an otherwise similar building with fully slatted flooring, the same plastic hanging toy was compared with a rootable particulate substrate provided in a hopper.

3 224 K. Scott et al. / Applied Animal Behaviour Science 99 (2006) Housing system Animals were housed in either a fully slatted (FS) or straw-based (ST) building, purpose built on the same site to an otherwise similar design (see MLC, 2004 for full details). Each house consisted of four rooms, each containing four pens. The ST pens measured 5.8 m 3.7 m, including the scrape-through passage, which was cleaned out daily whilst pigs were shut in the lying area. After cleaning out, fresh barley straw was added to the pens at the rate of 0.36 kg straw per pig per day. FS pens measured 5.5 m 3.7 m and had flooring of concrete slats with 83 mm width and 18 mm gap. The ventilation and environment in both housing systems was automatically controlled (Euromatic DOL34H, Skov, Denmark) to set maximum and minimum ventilation, relative humidity and temperature against occupancy day. Each room had two windows, allowing natural daylight, and artificial light was mainly used during husbandry tasks, weighing and behaviour observations. Pigs in both houses received the same liquid diets which were automatically fed ad libitum. Water was freely available from four nipple drinkers per pen Animals One thousand and twenty-four externally sourced (Large White Landra- Landrace) Large White pigs were received in eight equal batches of 128 over 12 weeks. The pigs had previously been housed in both slatted and straw-based accommodation and were approximately 12 weeks of age at entry. Batches were allocated alternately between the housing systems until all rooms were filled. After a 4-day period of acclimatisation to the housing system, each pig was ear tagged for individual identification and then weighed. The batch was divided into four groups of 32 pigs in order of weight. Each group was then randomly allocated to one of the four pens within a single room. Numbers per pen were reduced at week 6 (mid-point) to 25 in the FS system (0.8 m 2 per pig) and 20 in the ST system (1.1 m 2 per pig), in accordance with normal commercial stocking densities for these housing types. Pigs were slaughtered at approximately 104 kg liveweight. At entry, three entire males and three females in each pen were chosen as focal pigs for detailed behavioural scans. Focal animals were selected according to the following criteria: two pigs (one of each sex) at approximately median weight for the group, two within the upper quartile weight band and two within the lower quartile band. Only focal pigs were used for detailed investigations of behaviour Environmental enrichment treatments All environmental enrichment treatments, with the exception of the straw bedding, were introduced to pens at the end of the 4-day acclimatisation period. In both the straw-based and slatted housing system, half of the pens received additional enrichment in the form of the commercially available Bite-Rite (B-R) object (Ikadan System, Denmark). This consisted of a plastic cone with four protruding plastic chewing arms, and was suspended at pig level. In the ST system, the remaining pens were enriched only by the straw bedding. In

4 the FS system, the remaining pens were provided with a double-spaced hopper containing shreds of unmolassed sugar beet pulp (SBP) as a form of rootable enrichment. Each morning, any soiled substrate was removed from the hoppers and replenished as required. The mean daily addition of fresh SBP to maintain a constant availability in the hoppers was 0.5 kg per pen Behavioural measurements K. Scott et al. / Applied Animal Behaviour Science 99 (2006) Behavioural time budgets were recorded for three 2 h periods ( , , h) in the week of entry, week before group size reduction at approximately 60 kg (mid-point) and week before slaughter. Focal pigs were individually identified using stock marker spray and observations were carried out by a single observer. Scan samples were taken at 10 min intervals during each 2 h period according to a predetermined ethogram, based on the method of Day et al. (2002). This ethogram detailed the animal s posture, behaviour and the substrate that the behaviour was directed towards (Table 1). Table 1 Ethogram of behaviours used in the study (behaviours within each category were mutually exclusive) Behaviour Description Posture Standing Body weight supported by all four legs Sitting Body weight supported by front legs and hindquarters Kneeling Body weight supported by knees and hind-quarters Lying on side Body weight supported by side Lying on belly Body weight supported by belly Behaviour Inactive Motionless with eyes closed Alert Motionless with eyes open Feeding Eating from the feeder or chewing food Drinking Mouth in contact with the drinker and water being ingested Chewing substrate Substrate in mouth (with/without visible chews) Rooting substrate Displacing substrate with circular movements of the snout Nosing substrate Movement of snout along or close to a substrate Fighting Interacting aggressively with another pig Mounting Placing front hooves in the back of a standing pen-mate Eliminating Defecating or urinating Other Other unlisted activity Substrates Other pigs Any part of pen-mate Straw Straw bedding Pen component Any part of the pen Feeder Food trough Drinker Water drinker Enrichment Additional environmental enrichment device None Behaviour not directed at any substrate

5 226 K. Scott et al. / Applied Animal Behaviour Science 99 (2006) Statistical analyses For all data analyses, the pen was the experimental unit. Behaviour data were first collated and the frequency at which each category of the ethogram occurred was expressed as a percentage of the total number of observations. The possible effect of time was tested using repeated measures ANOVA; however, this revealed no statistical interaction between environmental enrichment treatment and time. Consequently, behaviour data were averaged across the three observation times. As the data were normally distributed, they were analysed by one way ANOVA (Minitab Release 13.1). Paired t-tests were carried out for specific valid comparisons within and between buildings; i.e. comparison of B-R manipulation in different housing systems and comparison of environmental enrichment types within the FS system only. 3. Results 3.1. Enrichment-directed behaviour Results for the mean percentage of observations that focal pigs performed the different behaviours are given in Table 2. Pigs in the ST system spent 16.1% of the observations in straw-directed behaviour. Whilst straw use decreased over time, this effect was not significant (week 1: 17.6%, mid-point: 16.8%, final week: 13.8% of observations, S.E.M. 1.65). The level of straw manipulation was not affected by the provision of additional environmental enrichment in the form of the B-R object. Levels of B-R manipulation were low in both housing systems when compared with levels of straw manipulation; however, FS pigs spent significantly more time manipulating the B-R object than ST pigs (P < 0.05). This difference in behaviour was reflected in the level of chewing damage to the devices when measured at the end of the experimental period (mean length of chewing arm remaining: FS = 16.7 cm versus ST = 22.2 cm, P < 0.001). Within the FS building, pigs spent more time in behaviour directed at the SBP than the B-R (P < 0.05), but both values were very low relative to the time spent in straw manipulation in the other building. Enrichment-directed behaviour decreased over time in the FS building (P < 0.05). This trend was more marked for the B-R (week 1: 1.8%, mid-point: 1.3%, final week: 0.3% of Table 2 Mean percentage of observations over three time periods that pigs spent engaged in behaviours directed at either straw or an available enrichment device (B-R = hanging Bite-Rite, SBP = sugar beet pulp shreds in hopper) Building enrichment Straw-based Fully slatted S.E.M. P-value Control +B-R +B-R +SBP % Behaviour towards Straw NS Enrichment device *** N = 8 pens for each treatment combination. *** P <

6 K. Scott et al. / Applied Animal Behaviour Science 99 (2006) Table 3 Mean percentage of observations over three time periods that pigs provided with different enrichment devices spent engaged in behaviours directed at pen-mates or pen components (B-R = hanging Bite-Rite, SBP = sugar beet pulp shreds in hopper) Housing enrichment Straw-based Fully slatted S.E.M. P-value Control +B-R +B-R +SBP % Behaviour towards Other pig NS Pen components *** N = 8 pens for each treatment combination. *** P < observations, S.E.M. 0.45) than for the SBP (week 1: 2.1%, mid-point: 2.5%, final week: 1.2% of observations, S.E.M. 0.45), but the interaction between enrichment and time was not statistically significant Pig- and pen-directed behaviours There were no significant effects of housing system or type of environmental enrichment on the level of behaviour directed at pen mates (Table 3). Pigs in the FS system spent more time in behaviours directed at pen components than pigs in the ST system (P < 0.001), irrespective of the type of additional enrichment provided. 4. Discussion The provision of additional environmental enrichment, either as shreds of unmolassed sugar beet pulp or as a Bite-Rite object, was unable to provide a comparable level of occupation to that of straw bedding. In accordance with findings from the present study, Van de Weerd et al. (2005) found that the level of straw manipulation was significantly higher in a straw-flow system compared with Bite-Rite manipulation in a part-slatted system. This was subsequently confirmed in a more critical comparison within the same building of straw-bedded pens and part-slatted pens with a Bite-Rite (Van de Weerd et al., 2006). Other studies have also indicated that various enrichment items provide less occupation than straw (Day et al., 2002). In an earlier study, Van de Weerd et al. (2003) identified the main characteristics of objects used most intensively by growing pigs (especially ingestible, odorous, chewable, deformable and destructible ) and suggested that these might be best suited to satisfy exploratory and foraging motivations. These findings are in accord with the results within the FS system in the present study, since SBP is an ingestible, chewable and destructible substrate, whilst the B-R only truly qualifies as chewable, although the shape and length of the chewing arms may be altered through intensive or prolonged use. The pig has evolved in semi-woodland areas, where it had to forage in the ground for food. Despite many generations of genetic selection, the pig still displays an inherent

7 228 K. Scott et al. / Applied Animal Behaviour Science 99 (2006) motivation to explore. Straw provides an outlet for the rooting and chewing activities that are part of the natural behavioural repertoire of pigs (Fraser et al., 1991). Arey (1993) considered straw a functional form of enrichment, since when given the opportunity, pigs will spend a considerable proportion of their time interacting with it (e.g. Edwards et al., 2004;Beattie et al., 2000;Jensen et al., 1993). The level of occupation provided by straw in the present study (16% of observations) is comparable to that reported previously in other situations (e.g. Jensen et al., 1993; McKinnon et al., 1989). The pigs natural tendency for exploration is still evident in barren environments, however, in such cases; manipulatory behaviour is channelled towards the limited number of available substrates (Rushen et al., 1993). Many studies (e.g. Lyons et al., 1995; Kelly et al., 2000; Guy et al., 2002) agree with the present findings, where the provision of straw reduced behaviour directed at pen components. The provision of straw has also been shown to reduce behaviour directed at pen-mates (e.g. Beattie et al., 2000; Kelly et al., 2000; Lyons et al., 1995), although this numerical tendency did not approach significance in the present study. In spite of the high levels of occupation which straw bedding can provide, work by Beattie et al. (1995) suggests that pigs have a preference for peat, mushroom compost and sawdust over straw. However, all these materials cause potential difficulties in slatted systems with liquid manure handling facilities. The use of a hopper to present the particulate substrate appeared to work well in the present experiment, but no assessment of wastage and consequent risk to slurry handling systems was made. Given that 91% of pig producers within the EU are still using part- or fully slatted systems (Hendriks et al., 1998), alternative forms of enrichment which are suitable for use in such systems must be sought. Whilst neither form of additional environmental enrichment in the present study was able to provide a comparable level of occupation to that of straw bedding, both were used to some extent throughout the finishing period; therefore, there is a definite value in providing some form of enrichment to pigs in fully slatted pens. Van de Weerd et al. (2005) reported decreased levels of Bite-Rite and straw manipulation over time. In the present study, manipulation of both forms of environmental enrichment and of the straw bedding decreased over time, although this trend was not significant in the case of straw. Replenishment of the straw on a daily basis may have enhanced its novelty value to the pigs. SBP, which was also replenished daily, showed less reduction in use over time than the B-R in the FS building, although a statistically significant interaction between enrichment and time was not demonstrated. 5. Conclusion Recent legislation has highlighted the urgency in identifying suitable enrichment that will meet the behavioural needs of the pig in slatted systems. At present, no such form of enrichment reliably provides the same level of occupation as seen with straw. The reasons behind the difference in occupation time between straw manipulation and enrichment object interaction require further study, since such occupation is important in the prevention of other adverse behaviours.

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