Tail amputation by tail docking or as an extreme consequence of tail biting in commercial pig production potentially has serious implications for animal welfare. Tail amputation causes peripheral nerve injury that might be associated with lasting chronic pain. The aim of this study was to investigate the short- and long-term effects of tail amputation in pigs on caudal DRG gene expression at different stages of development, particularly in relation to genes associated with nociception and pain. Microarrays were used to analyse whole DRG transcriptomes from tail amputated and sham-treated pigs 1, 8, and 16 weeks following tail treatment at either 3 or 63 days of age (8 pigs/treatment/age/time after treatment; n = 96). Tail amputation induced marked changes in gene expression (up and down) compared to sham-treated intact controls for all treatment ages and time points after tail treatment. Sustained changes in gene expression in tail amputated pigs were still evident 4 months after tail injury. Gene correlation network analysis revealed two co-expression clusters associated with amputation: Cluster A (759 down-regulated) and Cluster B (273 up-regulated) genes. Gene ontology (GO) enrichment analysis identified 124 genes in Cluster A and 61 genes in Cluster B associated with both “inflammatory pain” and “neuropathic pain.” In Cluster A, gene family members of ion channels e.g., voltage-gated potassium channels (VGPC) and receptors e.g., GABA receptors, were significantly down-regulated compared to shams, both of which are linked to increased peripheral nerve excitability after axotomy. Up-regulated gene families in Cluster B were linked to transcriptional regulation, inflammation, tissue remodeling, and regulatory neuropeptide activity. These findings, demonstrate that tail amputation causes sustained transcriptomic expression changes in caudal DRG cells involved in inflammatory and neuropathic pain pathways.
Dissertation: Friday 20 September 2019, 09.15 in Audhumbla, VHC, SLU Ultuna
Torun Wallgren defends her thesis “A tale of tails – prevention of tail biting in pigs by early detection and straw management”. View the live stream / recording
Torun Wallgren: A tale of tails – Prevention of tail biting by early detection and straw management
Opponent /external evaluator: Professor Nicole Kemper, Institute for Animal Hygiene, University of Veterinary Medicine Hannover, Germany
Professor Andrew Michael Janczak, Norwegian University of Life Sciences (NMBU), Oslo, Norway
Agr. Dr. Anne-Charlotte Olsson, Inst för Biosystem och Teknologi, SLU Alnarp
Professor Lotta Rydhmer, Professor, Inst för Husdjursgenetik (HGEN), SLU Ultuna
Professor Linda Keeling, Institutionen för husdjurens miljö och hälsa (HMH), SLU Ultuna (reserv).
Docent Stefan Gunnarsson, HMH, SLU Skara
Nils Lundeheim, Professor, HGEN, SLU Ultuna
Rebecka Westin, VMD, HMH, SLU Skara
Pigs in their natural environment spend the majority of their time exploring their surroundings through rooting, sniffing and chewing to find food and resting places. Rooting under commercial conditions is often fully dependent on the provision of rooting material. Lack of rooting opportunity may redirect the exploratory behaviour and cause tail biting, an abnormal behaviour that causes acute, long- and short-term pain. Tail biting is a common issue in modern pig production, reducing health, profitability and animal welfare. To fulfil pigs’ explorative needs, the Council Directive 2008/120/EC states that pigs should have permanent access to a sufficient amount of material, such as straw, to enable proper investigation and manipulation activities.
However, instead of improving pig environment to reduce tail biting, >90% of pigs in the EU are tail docked despite the prohibition of routine docking. Docked pigs have a less attractive and more sensitive tail tip and are less willing to allow biting. Docking aims at reducing the symptoms of tail biting rather than eliminating the cause. One argument for not increasing exploration through e.g. straw provision is fear of poor hygiene.
The overall aim of this thesis was to investigate the effect of straw on tail lesions, behaviour and hygiene (Studies I and II) as well as investigating tail position as a method for early detection of tail biting (Study III) in commercial production. Study I showed that 99% of Swedish farmers provide their pigs with straw (mediangrowers: 29 gram/pig/day; medianfinishers: 50 gram/pig/day). The amount of tail biting recorded at the abattoir was on average 1.7%. Study II showed that an increased straw ration decreased presence of tail wounds and initiated more straw-directed behaviour. Straw had little effect on hygiene. Study III showed that tail posture (hanging or curled) at feeding correctly classified 78% of the pigs with tail wounds. Less severe tail damage, e.g. swelling or bite marks, did not affect the tail posture.
The main conclusions are that increased straw reduces tail damage as well as pen-directed behaviours. Instead, straw increases straw-directed behaviours, while not affecting pig and pen hygiene negatively. Hence, it should be possible to rear pigs with intact tails without the use of tail docking in the EU.
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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).
PigProgress – Early indicators for tail biting in pigs Should pigs in the EU keep the end of their tails, or should tails be docked in the 1st days of the pigs’ lives to reduce risk of tail biting? The subject is widely discussed which also underlines that there is no easy answer. However, there is work in progress and so are some very promising results, writes pig welfare expert Vivi Aarestrup Moustsen. Read more in Pig Progress
By Emma Catharine Greenwood, William H. E. J. Van Wettere,
Jessica Rayner, Paul E. Hughes and Kate J. Plush, 2019. Animals 2019, 9(1), 8;
When sows are mixed into groups, hierarchies form and
resulting aggression and stress can affect production and welfare. This study
determined the effect of providing point-source materials on aggressive and
play behaviors in gestating sows. Large white cross Landrace sows were mixed
after insemination; six pens of 12 sows were housed in ‘standard’ pens, and six
pens of 12 sows were housed in ‘enhanced’ pens. The ‘enhanced’ pens each
contained two rubber mats, eight strands of 24 mm-thick sisal rope and two yellow
plastic disks, suspended from the roof. The sows remained in these pens until
pregnancy confirmation. Salivary cortisol concentration, injury counts, and sow
behaviors were recorded the day before mixing (day 1), mixing (day 0) and
post-mixing day 1, day 4, day 7 and day 20. At farrowing, reproductive outcomes
were obtained. Play was observed (including locomotor and object play) in the
‘enhanced’ pen, and percentage of time spent playing was greater on d4 (1.48 ±
0.3 Square root transformed data (2.84% non-transformed adjusted mean)), d7
(1.43 ± 0.3 (2.97%)) and d20 (1.64 ± 0.3 (3.84%)), compared to d0 (0.56 ± 0.3
(0.70%)) and d1 (0.87 ± 0.3 (1.67%) (p < 0.05)). No play was observed in
standard housing. Aggression, salivary free cortisol concentrations and
injuries were unaffected (p > 0.05). The provision of materials had no
impact on aggression, although their presence maintained sow interest and play
behavior, suggesting a positive effect.
By Torun Wallgren, Anne Larsen and Stefan Gunnarsson, 2019. Animals 210: 26-37. Special Issue Environmental Enrichment of Pigs.
Tail biting is a large welfare problem in modern pig
production, causing pain and reduced health and production. The identification
of tail biting is important for minimising the risk of the escalation of the
behaviour and its consequences. Tail posture (i.e., tail hanging or curled) has
been suggested to depend on the presence of tail wounds and, therefore, has
been suggested as an indicator of tail biting. This study investigated the
relationship between tail position and tail damages at feeding, since that
could be a feasible time for producers to detect tail posture. The experiment
showed that 94% of the pigs had curly tails and that pigs with wounds were more
likely to have hanging tails than pigs with nondamaged tails. By observing the
tail position at feeding, we were able to identify pigs with tail wounds in 68%
of cases simply by scoring pigs with hanging tails. To conclude, the scoring of
pigs with hanging tails at feeding was found to be a useful tool for
identifying tail damages, which may otherwise be difficult to detect by the
Tail posture (i.e., hanging or curled) has been suggested to
be an indicator of tail biting, and hanging tails predisposed to damage. The
aim of this study was to investigate if tail posture was feasible as a tail
damage indicator in a commercial setting. The study was carried out on one
batch of 459 undocked finishing pigs (30–120 kg in weight). Weekly scoring of
tail posture was combined with the scoring of tail lesions. Tail posture was
observed at feeding to facilitate the usage of the method in commercial
settings. A curly tail was observed in 94% of the observations. Pigs with tails
scored with “wound” were 4.15 (p < 0.0001) times more likely to have hanging
tails, and pigs scored with “inflamed wounds” were 14.24 (p < 0.0001) times
more likely to have hanging tails, compared to pigs with nondamaged tails. Tail
posture correctly classified tails with “wound” or “inflamed wound” 67.5% of
the time, with 55.2% sensitivity and 79.7% specificity, respectively. The
method of observing the tail position at feeding seems useful as a complement
to normal inspection for detecting tail biting before tail wounds are visible
to the caretaker.
Tail biting is a serious animal welfare and
economic problem in pig production. Tail docking, which reduces but does not
eliminate tail biting, remains widespread. However, in the EU tail docking may
not be used routinely, and some ‘alternative’ forms of pig production and
certain countries do not allow tail docking at all. Against this background,
using a novel approach focusing on research where tail injuries were
quantified, we review the measures that can be used to control tail biting in
pigs without tail docking. Using this strict criterion, there was good evidence
that manipulable substrates and feeder space affect damaging tail biting. Only
epidemiological evidence was available for effects of temperature and season,
and the effect of stocking density was unclear. Studies suggest that group size
has little effect, and the effects of nutrition, disease and breed require
further investigation. The review identifies a number of knowledge gaps and
promising avenues for future research into prevention and mitigation. We
illustrate the diversity of hypotheses concerning how different proposed risk
factors might increase tail biting through their effect on each other or on the
proposed underlying processes of tail biting. A quantitative comparison of the
efficacy of different methods of provision of manipulable materials, and a
review of current practices in countries and assurance schemes where tail
docking is banned, both suggest that daily provision of small quantities of
destructible, manipulable natural materials can be of considerable benefit.
Further comparative research is needed into materials, such as ropes, which are
compatible with slatted floors. Also, materials which double as fuel for
anaerobic digesters could be utilised. As well as optimising housing and
management to reduce risk, it is important to detect and treat tail biting as
soon as it occurs. Early warning signs before the first bloody tails appear,
such as pigs holding their tails tucked under, could in future be automatically
detected using precision livestock farming methods enabling earlier reaction
and prevention of tail damage. However, there is a lack of scientific studies
on how best to respond to outbreaks: the effectiveness of, for example,
removing biters and/or bitten pigs, increasing enrichment, or applying
substances to tails should be investigated. Finally, some breeding companies
are exploring options for reducing the genetic propensity to tail bite. If
these various approaches to reduce tail biting are implemented we propose that
the need for tail docking will be reduced.
• Prenatal stress (PNS) can have detrimental effects on
piglets behaviour and welfare.
• Pre-weaning enrichment may compensate negative effects of
PNS in piglets.
• PNS effects were delayed after weaning at d 27 as shown by
an increased inactivity.
• Enrichment had positive effects but its removal at weaning
• Pre-weaning enrichment did not compensate for the effects
Prenatal stress (PNS) can have detrimental effects on
behaviour and welfare, such as decreased exploration. Whether housing
enrichment before weaning compensate negative effect of PNS in commercial pigs
is unknown. To address this question, 44 sows were assigned to either a mixing
stress (T) or a control (C) treatment in mid-gestation. During lactation, half
of the T and C sows were housed with their 12-piglets litter in straw enriched
pens (E) while the others were housed in standard farrowing crates (S). At
weaning, 6 piglets per litter were selected and moved to non-enriched standard
pens. Lying down, exploration and social behaviour were recorded in the
home-pen before weaning (d 6, d 12, d 20), on the day of weaning (d 21), and
after weaning (d 22, d 27) using scan and one-zero samplings. Three piglets per
litter were individually subjected to a social isolation test and a social
confrontation test at d 17. Data were analysed by day using mixed models with
PNS, housing enrichment and their interaction as fixed effects. We found no
interaction between the treatments, suggesting the absence of a compensatory
effect of enrichment on PNS. Pre-weaning enrichment promoted exploration (P<
0.004) and seemed to improve comfort, as piglets spent more time lying down
(P< 0.02), but was associated with reduced locomotion and play fighting
(P< 0.03) compared to no enrichment. After weaning, E piglets explored less
(P< 0.01) and played less (locomotion and fighting play: P< 0.0003) than
S piglets. They also performed more belly-nosing at d 27 (P =0.04). These
results support the idea that the removal of enrichment at weaning negatively
affects piglets. The E piglets exhibited higher emotional reactivity than S
piglets (i.e. more high-pitched calls and escape attempts) during the social
isolation test, but no clear effect was observed during the confrontation test.
The effects of prenatal stress on behaviour were only apparent after weaning.
On d 27, T piglets spent more time lying (P =0.02), and showed reduced
exploration (P =0.004), locomotion play (P=0.03), fighting play (P=0.04) and
mounting behaviour (P =0.002) than C piglets. In conclusion, both prenatal
stress and pre-weaning enrichment affected piglet behaviour, but a compensatory
effect of enrichment on the negative effects of prenatal stress could not be
• Changes in tail posture can predict a tail biting outbreak
at pen level.
• Percentage of hanging tails in pens close to an outbreak
was almost doubled.
• A correlation between number of tail damages and lowered
tails were identified.
• No changes in activity was identified prior to a tail
Detecting a tail biting outbreak early is essential to
reduce the risk of pigs getting severe tail damage. A few previous studies
suggest that tail posture and behavioural differences can predict an upcoming
outbreak. The aim of the present study was therefore to investigate if differences
in tail posture and behaviour could be detected at pen level between upcoming
tail biting pens (T-pens) and control pens (C-pens). The study included 2301
undocked weaner pigs in 74 pens (mean 31.1 pigs/pen; SD 1.5). Tails were scored
three times weekly (wound freshness, wound severity and tail length) between
07:00 h–14:00 h from weaning until a tail biting outbreak. An outbreak (day 0)
occurred when at least four pigs had a tail damage, regardless of wound
freshness. On average 7.6 (SD 4.3) pigs had a damaged tail (scratches + wound)
in T-pens on day 0. Tail posture and behaviour (activity, eating, explorative,
pen mate and tail directed behaviour) were recorded in T-pens and in matched
C-pens using scan sampling every half hour between 0800–1100 h 1700–2000 h on
day -3, -2 and -1 prior to the tail biting outbreak in T-pens. Further, to
investigate if changes in tail posture could be a measure for use under
commercial conditions, tail posture was recorded by direct observation from
outside the pen. The live observations were carried out just before tail
scoring on each observation day until the outbreak. The video results showed
more hanging/tucked tails in T-pens than in C-pens on each recording day
(P < 0.001). In T-pens more tails were hanging on day -1 (33.2%) than on day
-2 (24.8%) and day -3 (23.1%). Further, the number of tail damaged pigs on day
0 was correlated with tail posture on day -1, with more tails hanging in pens
with 6–8 and >8 tail damaged pigs than in pens with 4–5 tail damaged pigs
(P < 0.001). Live observations of tail posture in T-pens also showed a
higher prevalence of hanging tails on day 0 (30.0%; P < 0.05) than on day
-3/-2 (17.2%), -5/-4 (15.4%) and -7/-6 (13.0%). No differences in any of the
recorded behaviours were observed between T-pens and C-pens. In conclusion,
lowered tails seem to be a promising and practical measure to detect damaging
tail biting behaviour on pen level even when using live observations. However,
there were no changes in activity, eating, exploration or tail-directed
behaviours prior to a tail biting outbreak.