The influence of time-unpredictable
and uncontrollable draught (forced cold air) on the behaviour of pigs
was observed in a climate-controlled pig house with two identical rooms
each with five pens. Two days after farrowing, pigs were matched
pairwise to correct for genetic, weight and sex differences, and weaned
at an average age of 35 days. From then on, the pigs in the experimental
room were submitted to draught in a time-unpredictable way. Days with
time-unpredictable draught were followed by days without draught.
studies started on Day 35 and ended on Day 75 of the experiment. The
total activity of the pigs was higher during draught (P<0.005).
Explorative behaviour was four times higher during draught periods than
during non-draught periods. Redirected explorative behaviour on
penmates, including earbiting, occurred more during draught periods (P<0.05). Agonistic behaviour increased strongly during draught periods (P<0.005); headknocks with biting as an excessive form of aggression occurred only during these periods.
Even in periods without draught, pigs in the experimental room had a sternum: recumbent lying ratio which was higher that that of pigs in the control room and lay in contact with penmates more than did pigs in the control room. Unpredictable and uncontrollable draught as a climatic stressor had enormous effects on the behaviour of pigs; redirected explorative behaviour on penmates and excessive aggression could be detrimental for health and the performance of pigs.
EC Directive 2001/93 requires that all pigs have access to proper investigation and manipulation materials. Intensively farmed pigs in Europe are frequently provided with a short/bare metal chain with or without an indestructible object attached to the chain. To date authorities are regarding this as proper enrichment. However, it has become increasingly clear that the chains do not provide proper enrichment, and that adding an indestructible object such as a ball, pipe or hard wood to the end of the chain may even reduce pig welfare. To test this hypothesis an expert survey was conducted. In total 36 international experts, mostly pig-welfare scientists, responded to the survey.
The experts only marginally agreed with the hypothesis (agreement
score 4.6 on average on a scale from 0-10). However, indestructible materials
generally received very low scores for welfare, indicating they did not provide
proper enrichment. Ranked from low to high average welfare score, the objects
were grouped in 5 significance levels:
Level 5 (totally insufficient): Chain hanging too high (for most
of the smallest pigs in the pen; average score 1.3 on a scale from 0 to 10
where 5.5 would be ‘acceptable’)
Level 4 (extremely insufficient): Short chain (3.1), Small
ball (2.8) and Big ball (average 2.5)
Level 3: (very insufficient) Pipe (3.5) and Bare chain (3.3)
Level 2-3 (very/rather insufficient): Hard wood (3.7)
Level 2 (rather insufficient): Chain on the floor (average:
Compared to the marginal enrichment provided before the EC Directive 2001/93 was implemented in 2007 (in the Netherlands generally a short/bare chain, scoring 3.1 and 3.3 respectively, i.e. Level 3-4), adding balls or pipe , as commonly done in The Netherlands and Germany, does not improve pig welfare. Hard wood, as practised esp. in the UK, is a most marginal improvement (only 0.4 higher on average than Bare chain). Chain on the floor scored a bit better (4.4), without being acceptable (set at 5.5). The ‘new’ Branched chains scored significantly better than all other indestructible materials and its welfare score (5.1 on average) was close to the pre-defined level of acceptability (5.5 on a scale from 0, worst, to 10, best). The welfare benefits of adding balls, pipes or hard wood to the metal chain were marginal, and well below what the experts considered acceptable enrichment. The branched-chains design, by contrast, appears to be the most viable alternative. It involves providing a longer chain, i.e. with the free end reaching to floor level, adding ‘branches’, i.e. several short chains ending at the nose height of the pigs, and providing more chains per pen (i.e. 1 branched chain per 5 pigs). Therefore, the implementation of current pig-enrichment legislation needs revision. Branched chains should be implemented widely (across the globe) and in the short term as a first step towards, and benchmark for, providing proper enrichment to intensively-farmed pigs.
See also the related publication and posts on this website:
Directive 2001/93 requires that all pigs have access to proper investigation
and manipulation materials. Intensively farmed pigs in Europe are frequently
provided with a short metal chain with or without an indestructible object
attached to the chain. To date authorities are regarding this as proper
enrichment, perhaps with (in)direct reference to the RICHPIG model as a
justification. However, it has become increasingly clear that the chains do not
provide proper enrichment, and that adding an indestructible object to the end
of the chain may even reduce rather than improve pig welfare. To test this
hypothesis an expert survey was conducted containing 26 more or less compound
questions. On a scale from 0 to 10 experts specified their level of agreement
with the hypothesis, the prevalence and welfare scores of nine indestructible enrichment
materials. In total 36 experts, mostly pig-welfare scientists, responded
(response rate: 39%). Indestructible objects are less prevalent in countries
that provide straw (like Sweden and the UK) and outside the EU (US). They are
more prevalent in the Netherlands, Belgium, France and Finland, while the
prevalence seems to be low in Spain. Balls, wood and pipes were provided most
frequently: hard wood especially in the UK (as specified in farm assurance); indestructible
balls and pipes in Germany and the Netherlands. The experts’ score for
agreement with the hypothesis was only 4.6 on average (scale 0-10; n=25). Enrichment
materials, ranked from high to low welfare score, were grouped in 5
significance levels as indicated by different superscripts based on Wilcoxon
signed rank tests: Branched chains (5.1a), Chain on the floor (4.4b),
Hard wood (3.7bc), Pipe (3.5c), Bare chain (3.3c),
Short chain (3.1d), Small ball (2.8d), Big ball (2.5d),
and Chain hanging too high (1.3e). Branched chains scored
significantly better than all other indestructible materials and its welfare
score (5.1 on average) was close to the pre-defined level of acceptability (5.5
on a scale from 0, worst, to 10, best). The welfare benefits of adding balls,
pipes or hard wood to the metal chain were marginal, and well below what the
experts considered acceptable enrichment. The branched-chains design, by
contrast, appears to be the most viable alternative. It involves providing a
longer chain, i.e. with the free end reaching to floor level, adding
‘branches’, i.e. several short chains ending at the nose height of the pigs,
and providing more chains per pen (i.e. 1 branched chain per 5 pigs). Branched
chains should be implemented widely and in the short term as a first step
towards, and benchmark for, providing proper enrichment to intensively-farmed pigs.
This post was published originally on the personal website of the first author (see here).
• Herbal compounds reduced the negative interactions and
• Environmental enrichment and herbal compounds increased
the body weight.
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.
• Spruce was consumed more quickly than other wood types.
• Pigs interacted with spruce more frequently than other
• No time effect was found on wood use.
• Replacement rate rather than cost may be a practical
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.
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.
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.
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.