Category Archives: Manipulation

Herbs and enrichment may benefit pig welfare

Influence of enrichment material and herbal compounds in the behaviour and performance of growing pigs. By Nicolau Casal-Plana, Xavier Manteca, Antoni Dalmau, Emma Fàbrega , 2018. Applied Animal Behaviour Science 195: 38-43.


• Environmental enrichment and herbal compounds can reduce stress in growing pigs.

• Environmental enrichment reduced stereotypies and redirected behaviour.

• Environmental enrichment increased exploratory behaviour.

• Herbal compounds reduced the negative interactions and body lesions.

• Environmental enrichment and herbal compounds increased the body weight.

Abstract Pigs reared in barren conditions are exposed to many different stressors, compromising their welfare and producing physiological and behavioural changes. The aim of this study was to assess the effect of environmental enrichment (EE) consisting of natural hemp ropes, sawdust, rubber balls, and a herbal compound (HC) of Valeriana officinalis and Passiflora incarnata on the behaviour and performance of growing pigs. Fifty-six pigs were used to assess four different treatments divided in two pens of seven animals per treatment (14 pigs/treatment). The treatments tested were: (a) pigs reared with EE, (b) pigs supplemented with HC, (c) pigs provided with both EE and HC, and (d) control group (CG, neither EE nor HC). Body weight and lesions were measured before starting the experiments (week 15) and at 18, 20, 22 and 24 weeks of age. Weekly instantaneous scan and continuous focal sampling were used to record behavioural patterns of activity, social interactions and abnormal behaviours. Three novel tests were carried out at 16, 19 and 23 weeks of age. Body weight at the end of the experiment was found to be significantly lower for the pigs reared in the control group compared to the other treatments (p = 0.0009). Furthermore, pigs reared with EE presented less stereotypies (p = 0.016) and redirected behaviour (0.0188), but more exploratory behaviour (p = 0.008). However, pigs supplemented with HC presented less social interactions (p = 0.048), a trend to present less negative social behaviour (p = 0.09) and less skin lesions (P = 0.0433) than pigs not supplemented. Finally, no remarkable differences were reported in any of the three novel tests. Thus, both EE and HC positively influenced some animal welfare indicators and performance of growing pigs in the present experiment.

Wood is a potentially suitable enrichment material for pigs

Use of different wood types as environmental enrichment to manage tail biting in docked pigs in a commercial fully-slatted system. By Jen-Yun Chou, Rick B. D’Eath, Dale A. Sandercock, Natalie Waran, Amy Haigh, Keelin O’Driscoll. 2018. Livestock Science 213: 19-27.


• Spruce was consumed more quickly than other wood types.

• Pigs interacted with spruce more frequently than other wood types.

• No time effect was found on wood use.

• Replacement rate rather than cost may be a practical concern.


Provision of adequate environmental enrichment on pig farms is a legal requirement under current EU legislation and also alleviates the risk of tail biting. Wood is an organic alternative where loose bedding, which has been identified as the optimal enrichment, is not possible on fully-slatted floors since it may disrupt the slurry system. The study compared four different wood types (beech (Fagus sylvatica), larch (Larix decidua), spruce (Picea sitchensis), and Scots pine (Pinus sylvestris L.)) as enrichment, taking into account the qualities of the wood, economic considerations, and effectiveness at reducing damaging behaviours and lesions. A total of 800 tail docked finisher pigs on an Irish commercial farm were used. Eight pens were provided with each wood type (25 pigs/pen), and the study was conducted over 2 replicates in time. In each pen a single wooden post was presented to the pigs in a metal dispenser with two lateral chains during the finisher period (12–22 weeks of age). The rate of wear, moisture content, and hardness of the wood along with lesion scorings and behavioural observation on pigs were monitored. Spruce was consumed more quickly than other wood types in terms of weight loss and reduction in length (P < 0.001), resulting in a greater cost per pig. Pigs were observed interacting with the spruce more frequently than the other wood types (P < 0.05). Pigs also interacted with the wood more often than the chains in spruce allocated pens (P < 0.001). Overall the interaction with wood posts did not decline significantly across time. However, there was no difference in the frequency of harmful behaviours (tail/ear/flank-biting) observed between wood types, and also no difference in the effectiveness of the different types of wood in reducing tail or ear damage. There was a positive correlation between ear lesion and tear-staining scores (rp= 0.286, P < 0.01), and between tail lesion and tail posture scores (rp= 0.206, P < 0.05). Wood types did not affect visceral condemnation obtained in the slaughterhouse. Wood is a potentially suitable enrichment material, yet the wood species could influence its attractiveness to pigs.

Enrichment may be joyful and reduce stress in young pigs

Pre-weaning environmental enrichment increases piglets’ object play behaviour on a large scale commercial pig farm. By Chung-Hsuan Yang, Heng-Lun Ko, Laura C. Salazar, Lourdes Llonch, Xavier Manteca, Irene Camerlink, Pol Llonch, 2018. Applied Animal Behaviour Science 202: 7-12 Environmental enrichment is a legal requirement for European pig farms. The suitability of enrichment materials for neonatal pigs is understudied and has not been tested in commercial settings. This study investigates the effect of hanging objects and substrate as two enrichment strategies pre-weaning, and compares the effect of these enrichment objects on play behaviour, aggression, growth and stress coping ability during lactation until 10 days after weaning. Farrowing crates were equipped with either six hanging objects (OB), a substrate box with wood bark (SUB), or nothing (control; CON). The behaviour of over 600 piglets (∼210 piglets/treatment) was recorded weekly by instantaneous scan sampling (10 s/piglet, repeated 6 times per day for 6 days). Aggression was monitored through skin lesions on focal piglets on 1 day before weaning and 1 and 2 days after weaning. Piglets were weighed individually every week. Stress coping ability was assessed through salivary cortisol from a sample of six piglets per litter on 1 day before (baseline), and on days 1 and 2 after weaning. Both enrichment groups showed more object play during lactation as compared to the control group (P < 0.001). The amount of object play increased linearly with age (P < 0.001). Enrichment did not affect social play or locomotor play during lactation. Enrichment did not influence the amount of skin lesions before weaning, but heavier piglets had more skin lesions (P < 0.01). The enrichment strategies had no influence on weight gain at any stage. The baseline of the salivary cortisol concentration was similar amongst the treatment groups; however, the cortisol concentration of the object group and control group was significantly higher at one day after weaning than at baseline (P < 0.001) whereas the substrate group showed no significant increase. In conclusion, providing either hanging objects or substrate alone could encourage neonatal piglets to express more object play behaviour. Compared to the hanging objects, providing substrate in the commercial neonatal environment demonstrated to decrease piglets’ stress at weaning, and therefore increase animal welfare.

Simple enrichment block may improve pig welfare

Enrichment in the Sucker and Weaner Phase Altered the Performance of Pigs in Three Behavioural Tests. By Cameron Ralph, Michelle Hebart and Greg M. Croninm 2018. Animals 8: 74.


We tested the hypothesis that provision of enrichment in the form of enrichment blocks during the sucker and weaner phases would affect the behaviour of pigs. We measured the performance of pigs in an open field/novel object test, a maze test, an executive function test and the cortisol response of the pigs after exposure to an open field test. The provision of enrichment blocks altered the behaviour of the pigs in all three tests and these changes suggest an increased willingness to explore and possibly an increased ability to learn. The behavioural tests highlighted that young pigs have the capacity to learn complex tasks. Our findings support the notion that the benefits of enrichment cannot be evaluated by measuring the interactions the animal has with the enrichments in the home pen and it may simply be beneficial to live in a more complex environment. We have highlighted that the early rearing environment is important and that the management and husbandry at an early age can have long-term implications for pigs. The enrichment we used in this study was very simple, an enrichment block, and we provide evidence suggesting the provision of enrichment effected pig behavioural responses. Even the simplest of enrichments may have benefits for the welfare and development of young pigs and there is merit in developing enrichment devices that are suitable for use in pig production.

Branched chains as enrichment for pigs (technical description, pictures and video)

This post illustrates the so-called branched chain design. This is an improved type of chain that seems most suited as a starting point towards providing proper enrichment (as required by e.g. EU legislation) for conventional, intensively-farmed pigs. However, also pigs on straw may benefit from such chains. Below the description of the branched chain design you can find some pictures and video clips of branched, anchor-type chains for pigs (conventionally-housed weaners and growing fattening pigs, and gilts kept on straw).

Specification of the branched chain design

1: Object-design: A branched chain consists of a vertically-positioned long chain with its end resting on the solid floor over a distance of 20 cm. Two or three additional chain ends (branches) end at or slightly below the nose height of the smallest and middle-sized pigs reared in the pen.
2: Material: The chains are stainless-steel anchor chains (for at least the last 5-10 links of each chain end). Recommended dimensions are 7mm for growing-fattening pigs, 5-6 mm for weaners, 4-5 mm for piglets and 8 mm for sows.
Anchor chains have links which are more round and heavier than the cheaper, more oval-shaped c-chains. Note that the indicated sizes refer to the diameter of the metal, not the diameter of the links. For example, a 7 mm anchor chain for finishers has links measuring 36×23 mm.  Preferably various chain sizes should be provided in the pen, esp. when the pen may contain pigs of variable sizes (e.g. from 25 to >100 kg). Stainless-steel anchor chains are more expensive, but only the last 5 or so links need to be replaced when worn e.g. every 5 – 10 years.
3: Availability and placement: One branched chain is provided for every 5 pigs.The chains are spaced apart as much as possible, preferably with at least one pig length between 2 branched chains in a pig pen. The branched chains are attached at the top end of the pen wall, over the solid floor, and not in the dunging area.

The description of the branched chain design was derived from: Bracke MBM, 2017. Chains as proper enrichment for pigs (incl. supplement). In: Spinka M, editor. Advances in Pig Welfare: Elsevier.

Table. Anchor-chain link dimensions

Chain link thickness (mm) Length (mm) Width (mm)
4 26.5 16
5 ~28 ~17.5 (estimate)
6 30 19
7 36 23
8 40 26
9 ~44 ~30 (estimate)
10 48 34

Pictures of branched anchor-type chains

Short chain and ball. Note the bite marks on the ball. The ball is hanging on a c-chain (oval shaped). The short chain resembles an anchor chain but isn’t (links not massive enough). Short chain, ball and branched chain made of suboptimal c-chain links. This type of branched chain uses only 1 fixation point (reducing costs). Branched anchor-type chain with 3 branches. Only top left branch is made of c-chain in order to ‘test’ pig preferences for the anchor-type chains (top right branch).
Four stainless-steel anchor chains. Two middle chains are worn by long-term use (5-10 years). Outer chains show original shape. Branched chain provided to weaned piglets Occasionally a pig will be reaching up. But normally they show downward-directed behaviour.
Branched chain for fatteners Most manipulation of the branched chains is floor directed. Both rooting and biting/chewing/playing.
Floor directed ‘rooting’. The pig’s nose really ‘fits’ a floor-directed orientation.
Also some more horizontal chewing Sometimes more pigs are interested in the same thing.
Side-way chewing (fits into cheek fold for canine teeth). Taking a whole branch (10 links) into the mouth. Three pigs all at once.
Some occasional pulling. Empty straw-bricket container. The floor plate may be used to keep a chain from getting stuck in the slats and/or repair when the floor below the branched chain gets worn. Gilt in a straw pen next to a branched chain between the lying area (front) and dunging area in the back of the pen.
Floor-directed chain manipulation may be labelled ‘rooting’ …  …not just because there is also some straw…  …it resembles stone chewing seen in outdoor sows.
A second branched chain in the same pen containing four gilts. Grabbing the chain horizontally, showing the cheek fold. A branched chain in another pen containing two gilts on straw.
Floor directed behaviour Biting the chain occasionally. Fixation of the floor chain using the right front leg. True ‘manipulation’ (as manus in Latin means ‘hand’).
Branched chain worn temporarily as an ‘ear ornament’. Two gilts playing with the branched chain at the same time. Anchor-chain links worn (right) by pig manipulation.





These pictures may be used for non-commercial purposes & publications provided copy-rights (MB) are acknowledged.

The video clips below show the pigs in action.

This video shows that a hockey-type ball may be frustrating for pigs, and that the branched chain design is much more appreciated, even by organic pigs.

Related posts:

Chains as enrichment for pigs (Book chapter with supplement)
Ketting als hokverrijking voor varkens (incl. link naar het supplement)
Pig animation – Improved, branched chain design as proper enrichment for pigs
Branched chains as enrichment for pigs (technical description, pictures and video)
Proper enrichment for intensively-farmed pigs – From review to preview
A collection of pictures of other enrichment materials for pigs can be found here: Prize contest (Prijsvraag) 2011.
Do pigs play with chains? Science versus society