Category Archives: Brain

Characterization of short- and long-term mechanical sensitisation following tail docking in pigs

Characterization of short- and long-term mechanical sensitisation following surgical tail amputation in pigs. By Pierpaolo Di Giminiani, Sandra A. Edwards, Emma M. Malcolm, Matthew C. Leach, Mette S. Herskin & Dale A. Sandercock. 2017. Nature Scientific Reports.

Commercial pigs are frequently exposed to tail mutilations in the form of preventive husbandry procedures (tail docking) or as a result of abnormal behaviour (tail biting). Although tissue and nerve injuries are well-described causes of pain hypersensitivity in humans and in rodent animal models, there is no information on the changes in local pain sensitivity induced by tail injuries in pigs. To determine the temporal profile of sensitisation, pigs were exposed to surgical tail resections and mechanical nociceptive thresholds (MNT) were measured in the acute (one week post-operatively) and in the long-term (either eight or sixteen weeks post-surgery) phase of recovery. The influence of the degree of amputation on MNTs was also evaluated by comparing three different tail-resection treatments (intact, ‘short tail’, ‘long tail’). A significant reduction in MNTs one week following surgery suggests the occurrence of acute sensitisation. Long-term hypersensitivity was also observed in tail-resected pigs at either two or four months following surgery. Tail amputation in pigs appears to evoke acute and sustained changes in peripheral mechanical sensitivity, which resemble features of neuropathic pain reported in humans and other species and provides new information on implications for the welfare of animals subjected to this type of injury.

See also our article in PigProgreess.

Histological and neurophysiological pain assessment in young pigs

Original title: Approche histologique et neurophysiologie de la douleur liée à la coupe de queue chez les porcelets

Presentation of Dr. Dale Sandercock (SRUC) at a seminar on histological and neurophysiological approaches to pain assessment in young pigs. INRA-PEGASE, St-Gilles, France, December 14th 2015


Concerns exist over the long term consequences of tail docking on possible tail stump pain sensitivity due to the development of traumatic neuromas in injured peripheral nerves. Traumatic neuroma formation may cause detrimental sensory changes in the tail due to altered peripheral and spinal neuronal excitability leading to abnormal sensation or pain. We have investigated tail injury and traumatic neuroma development by histopathological assessment after tail docking and measured the expression of key neuropeptides associated with peripheral nerve regeneration, inflammation and chronic pain. In complimentary studies on tail docking and tail biting, we have developed behavioural assessment approaches to measure mechanical nociceptive thresholds (MNT) in the pig tail in purpose built test set-up using a Pressure Application Measurement (PAM) device. Using these approaches we have determined baseline MNT in intact tails along different regions of the tail and also measured changes in MNT over time in pig with resected tails (simulation of the effect of tail biting). An overview of other Scotland’s Rural College (SRUC) pig health and welfare research projects is also presented.

Presentation Pic INRA seminar on pain (D Sandercock, 2015))

Preliminary study on tail nerves in piglets after tail docking

Carr, R.W., J.E. Coe, E. Forsch, M. Schmelz, D.A. Sandercock, 2015. Structural and functional characterisation of peripheral axons in the caudal nerve of the neonatal pigs: Preliminary data. Proceedings of the 9th EFIC Congress, Vienna, Sept 2-5.


The pig tail is innervated by the caudal tail nerves and it is evident at the site of injury after tail docking (i.e. 8/9th caudal vertebrae) that a relatively high proportion of both C and A-fibres can be affected following peripheral nerve transection, with implications for axonal excitability and nociceptive processing in the tail stump.
As a proof of principle, it is possible to assess A- and C-fibre axonal function using electrical axonal excitability techniques for pig caudal tail nerve. In neonatal caudal nerves, A and C-fibre axons show significant changes in conduction speed which are related primarily to neonatal age.
Future studies will examine axonal functional properties in pig tails later in life where traumatic neuroma formation in the caudal nerves is present.

Annotated TEM micrograph of tail nerves (Dale Sandercock)


Structural and functional characterisation of peripheral axons in the caudal nerve of the neonatal pigs: Preliminary data
R.W. Carr1, J.E. Coe2, E. Forsch1, M. Schmelz1, D.A. Sandercock2
1Department of Anaesthesiology, University of Heidelberg, Mannheim, Germany
2Animal and Veterinary Science Research Group, Scotland’s Rural College (SRUC), Easter Bush, United Kingdom

Background and aims: Early postnatal tail docking (amputation of 2/3rds of the tail) in piglets is performed as a preventative measure to minimize potential trauma associated with tail biting in older animals. The aim of this study was to investigate caudal nerve axonal composition and the effects of tail docking on axonal function in neonatal pigs.
Methods: Axonal composition was examined using Transmission Electron Microscopy (TEM). Functional assessment of A and C-fibre axons was performed in vitro using compound action potential (CAP) recordings from isolated nerve fascicles.
Results: TEM revealed both myelinated and unmyelinated axons in dorsal and ventral caudal nerves. Myelinated axons ranged in size from small diameter thinly myelinated Aδ-axons to larger diameter Aβ-axons (mean 2.30; range 0.7-6.3 μm). Unmyelinated C-fibre axons clustered together in multiple Remak bundles (mean 0.7; range 0.3-1.9 μm). Caudal nerves were harvested for functional assessment at 5 days of age from undocked tails and at 12.3 days (i.e. 9.3 days after docking) from docked pigs. The average A-fibre CAP amplitude from undocked tails was larger (1599.6±552.9μV) and conducted more rapidly (9.79±2.04m/s) than the A-fibres from docked tails (amplitude 1065.1±507.6μV and c.v.=7.78±2.57m/s). For C-fibres, the average axonal conduction velocity in docked tails was slower (1.74±0.2m/s) than in undocked tails (2.26±0.41m/s). Axonal conduction in caudal nerve C-fibres from both intact and docked animals was completely blocked by 500 nM tetrodotoxin (TTX) suggesting conduction was mediated primarily by TTX-sensitive NaV-isoforms.
Conclusions: As a proof of principle study, it is possible to functionally assess A- and C-fibre axons in pig caudal nerve using electrical axonal excitability techniques.
Acknowledgments: ANIWHA.

Poster Carr et al. 2015

Rat race to pigs without tail biting problems

Success is not certain but if you do nothing, failure is” Paul Ulasien
April 8 2015, written by Dr Nanda Ursinus, Adaptation Physiology Group, Wageningen University, The Netherlands

Damaging biting behaviours such as tail biting expressed by pigs is a huge problem in husbandry systems as it reflects and causes severe health and welfare problems, and economic losses. Many organisations world-wide focus on preventing and reducing these unwanted behaviours and so does Wageningen University and Research Centre, the Netherlands. During the Paris meeting of the Farewelldock-team (April 8 2015), a number of past, present and (possibly) future projects in which the  Adaptation Physiology Group of Wageningen University is involved, were presented that incorporate the problem of tail biting in pigs. In this blog two of the projects will be introduced: 1. A PhD trajectory entitled ‘A tale too long for a tail too short: Identification of characteristics in pigs related to tail biting and other oral manipulations directed at conspecifics’; 2. A project based on the Dalfsen Declaration: ‘Curly tails, the Dutch approach’.

A tale too long for a tail too short

Identification of characteristics in pigs related to tail biting and other oral manipulations directed at conspecifics

fwc blog NU phd tale too long 220415

In 2010 Nanda Ursinus started her PhD trajectory and had as main aim to identify biological characteristics of barren and enriched housed pigs that relate to their tendency to develop these damaging oral manipulative behaviours. The project was supervised by Professor Bas Kemp and Dr Liesbeth Bolhuis of the Adaptation Physiology Group, and Dr Kees van Reenen of Wageningen UR Livestock Research. In October 2014 the project finished by defending the thesis in front of an international committee.

The project showed that tail biting behaviour in intensively kept piglets with undocked tails can start as early as the lactation period leading to small tail wounds (± 10% of 480 piglets) observed at time of weaning (i.e. 4 weeks of age). Tail damage was largely prevented by providing straw-bedding, but tail wounds were not fully eliminated (1 pig out of 240 pigs was removed due to a tail wound) (Ursinus et al. 2014 Appl Anim Behav Sci 156:22-36). As straw-bedding is not suitable in many intensive pig husbandry systems, the use of jute sacks as enrichment device was explored. In partly docked gilts, jute sacks were able to reduce the presence of tail wounds five-fold and reduced the occurrence of damaging biting behaviours up to 50%. Furthermore, jute sacks tended to reduce damage to the sows’ tail inflicted by piglets (Ursinus et al. 2014 J Anim Sci 92:5193-5202). Post-weaning, tail biting pens could be predicted by an increased activity and increased levels of pig and pen-directed (e.g. jute sack usage) oral manipulative behaviours (Ursinus et al. 2014 Appl Anim Behav Sci 156:22-36; Camerlink et al. 2015 Behav Genet 45:117-126). Displaying tail biting behaviour by individual pigs is often temporary and consequently inconsistent over time; once a tail biter is not always a tail biter (Ursinus et al. 2014 Appl Anim Behav Sci 156:22-36). There seems to be one exception to this rule: gilts that were identified as high-tail biters during the rearing phase, were identified as high-tail biters during the nursery phase as well (Ursinus et al. 2014 J Anim Sci 92:5193-5202). This suggests that obsessive tail biters (as previously described by Taylor et al. 2010 VET J 186:137–147) may be more consistent in displaying tail biting behaviour than other types of tail biting behaviour. The main hazard in this is that obsessive tail biters are only occasionally present on farms and consequently but not surprisingly, it was hard to identify individual behavioural predictors of tail biting pigs. However, tail biters were likely to stem from a litter with a relatively high level of tail biting behaviour (Ursinus et al. 2014 Appl Anim Behav Sci 156:22-36). Additionally, in a spin-off project with piglets (n=160) that received a jute sack for three days (starting at 15 days of age), individual jute sack manipulation (i.e. nosing, chewing and rooting) turned out to be promising in terms of predicting biting behaviours (mainly directed at other body parts than the tail or ears) at 12 weeks of age (in preparation). We also studied pig personality a bit closer; although there are indications that tail biters would be active copers during stressful situations, our study did not find consistent evidence for that. However, our results suggested a higher level of fearfulness expressed during a novel object test in tail biting pigs. This finding was accompanied with lower blood platelet serotonin levels (i.e. a neurotransmitter involved in for instance mood) in tail biting pigs (Ursinus et al. 2014 PloS One 9:e107040). In a previous study, we also found signs that blood platelet serotonin and serotonin activity in the right hippocampus were related to a pig’s fearfulness (Ursinus et al. 2013 Physiol Behav 118:88–96). Our findings perfectly matches literature about mental disorders in humans and behavioural abnormalities in other animal species (e.g. feather pecking in laying hens). Tryptophan (i.e. the precursor of serotonin) is involved in many biological processes, also in for instance the most important production parameter in pigs: growth. Both phenotypic and genetic production parameters pointed in the direction of an association with (tail) biting behaviours in gilts (Ursinus et al. J Anim Sci 92:5193-5202) implying that pigs are searching for something with a nutritional value, possibly tryptophan. Although tail biting behaviour is not as consistently displayed in individual animals as previously expected and the environment seems to play a large (or even the largest) role in the development of damaging biting behaviours, the results show that also the role of genetics cannot be ignored. Up until now it is difficult to capture the level of expressed tail biting in direct breeding values. However, indirect breeding values or ‘indirect genetic effects’ have been associated with tail damage. Pigs differ in their heritable effect on their group mates’ growth and pigs with a positive effect on their group mates’ growth were found to cause less tail damage (Camerlink et al. 2015 Behav Genet 45:117-126). Tail biting behaviour in pigs thus seems to be caused by a variety of temporary states and more stable traits that influence their motivation to display foraging and exploratory behaviours. Preventing and reducing such unwanted behaviours requires a joint effort of science, industry and society to optimize housing conditions, feeding, management and breeding of pigs.

For more information you can contact Nanda Ursinus (Nanda . ursinus @ wur . nl or Nanda . ursinus @ gmail . com) or Liesbeth Bolhuis (Liesbeth . bolhuis @ wur . nl). This project was funded by the Dutch Ministry of Economic Affairs, and it was a collaboration with the Dutch ‘Sociable Swine’ project. In the Sociable Swine project four PhD trajectories were finished:

  1. Sociable swine: Indirect genetic effects on growth rate and their effects on behaviour and production of pigs in different environments. Irene Camerlink, 2014.
  2. (Em)pathetic pigs? The impact of social interactions on welfare, health and productivity. Inonge Reimert, 2014.
  3. Sociable Swine: Prospects of indirect genetic effects for the improvement of productivity, welfare and quality. Naomi Duijvestein, 2014.
  4. Engaging Society in Pig Research: A multi-stakeholder approach to enhance animal welfare in pig production. Marianne Benard, 2014.


fwc blog NU phd Sociable swine 220415fwc blog NU phd Empathic pigs 220415

Sociable swine (Duijvestein)Engaging society

 Dalfsen Declaration

Curly tails, the Dutch approach

In 2012, a group of Dutch stakeholders in the pig farming sector joined forces in an attempt to find ways to reduce the need for tail docking in pigs kept in the Netherlands. Therefore they developed and signed a Declaration, now called the ‘Dalfsen Declaration’. Declaration partners involve the industry (Dutch Federation for Agriculture and Horticulture (LTO), Dutch union of Pig Producers (NVV), Coppens Animal Feed, Topigs (now Topigs Norsvin), Royal Netherlands Veterinary Organisation (KNMvD) and Vion Food Group), an NGO (Dutch Society for the Protection of Animals), and a research centre (Wageningen University and Research Centre: Department of Animal Sciences and Wageningen UR Livestock Research). The ambition of this stakeholder-group was supported by the Dutch Ministry of Economic Affairs and several other parties in the pig chain. During the course of time 3 routes are followed: 1. A demonstration project, 2. Creating a network of Dutch front runners, and 3. Stepwise increasing the tail length.

The demonstration project started end 2013 at Pig Innovation Centre Sterksel (VIC Sterksel), the Netherlands, and likely ends in December 2015. The project allows animal caretakers to practice with a number of enrichment materials and to learn understanding the behaviour and especially the tail posture of pigs. Enrichment materials used were sometimes rather complex (such as straw or grass silage) and at other times less complex (such as a rope or straw pellets). The materials were provided on the floor, at the walls, or hung from the ceiling and eventually need to be valued by the caretakers as easily applicable in Dutch (intensive) husbandry systems. Enrichment is used both as a preventive and curative measure. As many pig farmers are in search of especially curative measures it is highly important to assess if enrichment materials are suitable in ending or at least reducing the severity of ongoing tail biting outbreaks. In 2015, a start-up meeting was organised with a group of enthusiastic front runners that keep pigs with long tails or are willing to try increasing the length of the tails of (some of) their pigs. During this meeting farmers gave insight in what they need (on their own farm) in order to be able to keep pigs with longer tails. These farmers will be guided and their actions will be monitored. The main ambition is to stepwise increase the length of pig tails in the Netherlands by gradually docking less. Collaboration with neighbouring countries is desired and therefore first steps are made by the Dutch Ministry of Economic Affairs to assess if (the Ministries of) Germany and Denmark share the vision of the Dalfsen Declaration Partners and are willing to join forces as well.

Contact person of the Dutch Curly tails project is Geert van der Peet (geert . vanderpeet @ wur . nl).

Pigs rooting on the floor

Tail docking in pigs alters gene expression in the brain associated with increased anxiety-like behaviour

Oberst et al. (2015) presented a poster on the effect of tail docking in neonatal pigs on the expression of genes involved in modulating anxiety-like behaviour at the annual meeting of the Scandinavian Association for the Study of Pain (SASP) at the Karolinska Institute, Stockholm, Sweden (13-14th April 2015).

The abstract is presented below; the poster can be found here


Background: Adverse experiences in early life, such as exposure to stress, can have long term detrimental effects on the future physiology and behaviour of the animal. Typically animals exposed to such experiences are more anxious and more reactive to stress in later life. Tail biting is a major problem in modern pig production, both in terms of animal welfare and productivity. Tail docking in early postnatal life is common practice to reduce risk of this problem, but causes pain and may alter pain sensitivity.

Aims: To investigate whether a significant painful experience in early life (tail docking) alters the expression of genes in the amygdala that are linked to an anxiety-prone phenotype.

Methods: Eight female piglets (Landrace/Large White x synthetic sireline) were used. Four piglets were tail docked (amputation of approx. 2/3 of the tail) on post-natal day 3 using hot-iron cautery and four sham-docked piglets served as intact controls. On post-natal day 10, pigs were sedated and then euthanized by barbiturate overdose. Brains were removed, the amygdala grossly dissected and frozen on dry ice. 20μm sections were cut and subsequently processed using in situ hybridisation with radiolabelled probes complementary to corticotropin-releasing hormone receptor-1 (Crhr1) and CRH receptor-2 (Crhr2) mRNA.

Results: Crhr1 mRNA expression was significantly greater (p<0.05) in the amygdala of tail-docked piglets compared with the sham-docked animals. There was no significant difference detected in Crhr2 expression in the amygdala between the groups.

Conclusion: Increased expression of Crhr1 in the amygdala is associated with an anxiety-prone phenotype in rats and pigs, thus it is likely that tail docking in early life leads to enhanced anxiety which may have a negative impact on pig welfare. Ongoing experiments will determine whether these central changes in gene expression are long-lasting.

[Support: BBSRC, DEFRA-part of ANIWHA ERA-NET initiative].

Oberst, P., D.A Sandercock, P.Di Giminiani, S.A. Edwards, P.J. Brunton, 2015. The effect of tail docking in neonatal pigs on the central expression of genes involved in modulating anxiety-like behaviour. Abstract for the poster presentation at the Scandinavian Association for the Study of Pain (SASP) Annual Meeting, Karolinska Institute, Stockholm, Sweden. 13-14th April 2015.


Neuroanatomical changes in pig tails following tail docking

Herskin et al. (2015) studied the formation of neuroma’s in pigs after tail docking.


In pig production, piglets are tail docked at birth in order to prevent tail biting later in life. In order to examine the effects of tail docking and docking length on the formation of neuromas, we used 65 pigs and the following four treatments: intact tails (n=18); leaving 75% (n=17); leaving 50% (n=19); or leaving 25% (n=11) of the tail length on the pigs. The piglets were docked between day 2 and 4 after birth using a gas-heated apparatus, and were kept under conventional conditions until slaughter at 22 weeks of age, where tails were removed and examined macroscopically and histologically. The tail lengths and diameters differed at slaughter (lengths: 30.6±0.6; 24.9±0.4; 19.8±0.6; 8.7±0.6 cm; P<0.001; tail diameter: 0.5±0.03; 0.8±0.02; 1.0±0.03; 1.4±0.04 cm; P<0.001, respectively). Docking resulted in a higher proportion of tails with neuromas (64 v. 0%; P<0.001), number of neuromas per tail (1.0±0.2 v. 0; P<0.001) and size of neuromas (1023±592 v. 0 μm; P<0.001). The results show that tail docking piglets using hot-iron cautery causes formation of neuromas in the outermost part of the tail tip. The presence of neuromas might lead to altered nociceptive thresholds, which need to be confirmed in future studies.


Herskin, M.S., Thodberg, K., Jensen, H.E. 2015. Effects of tail docking and docking length on neuroanatomical changes in healed tail tips of pigs. Animal 9: 677-681.
Tail docking causes neuroanatomical changes to pig tails, PigProgress, 25-3-2015

Tail docking using hot iron cautery

Grimace scale


With the increase in attention to animal welfare, researchers have focused their interest on the assessment of pain in farm animals. In humans who cannot self-report, such as infants and unconscious patients, the observation of facial expression is frequently used for pain assessment (Prkachin, 2009). The possibility to assess pain through changes of facial expression has also been studied in animals, and pain scales developed which include the ‘Mouse Grimace Scale’ (Langford et al., 2010), the ‘Rat Grimace Scale’ (Sotocinal et al., 2011) and the ‘Rabbit Grimace Scale’ (Keating et al., 2012). Although with some species differences, the three scales focus on the eyes, nose, cheeks, ears and whiskers of an animal.
Although pigs have fewer muscles for facial expression, there are subtle changes in appearance (Flecknell & Watermann-Pearson 2000), but there are currently no published pain scales based on facial expression in pigs. The aim of this research was to investigate if it is possible to observe changes in piglets’ facial expressions immediately after painful procedures. Thirty-one piglets were subjected to tail docking by cautery, while held by the farmer. Images of faces were taken immediately before and after this procedure. These images were sorted and those in which piglets had closed eyes were excluded.
Images were evaluated by two treatment-blind observers, scoring from 0 to 2 (0 was no evident tension and 2 very evident tension).
Because of the non normal distribution, data were analysed with the non-parametric Wilcoxon Signed Rank Test, which showed that the cheek tension score significantly increased from before to after the procedure (P<0.042). This result shows promise for the adoption facial expression as a tool for acute pain assessment in pigs.
Facial expression of piglet
In piglets subjected to tail docking cheek tension score significantly increased from before to after the procedure (P<0.05)

Reference: Lonardi, C., Leach, M., Gottardo, F., Edwards, S. 2013. The ‘Grimace Scale’: do piglets in pain change their facial expression? Proceedings of the Joint Meeting of the 5th European Symposium of Porcine Health Management and the 50th Anniversary Meeting of the Pig Veterinary Society of Great Britain, Edinburgh, UK, 22nd – 24th May 2013.

Tail biting changes the pig brain

A recent paper by Valros et al. (2015) shows evidence for changes in monoamine metabolism in the brains of pigs affected by tail biting, both in the victims and the biting pigs.

Dissection of a pig brain


Tail biting in pigs is a major welfare problem within the swine industry. Even though there is plenty of information on housing and management-related risk factors, the biological bases of this behavioral problem are poorly understood. The aim of this study was to investigate a possible link between tail biting, based on behavioral recordings of pigs during an ongoing outbreak, and certain neurotransmitters in different brain regions of these pigs. We used a total of 33 pigs at a farm with a long-standing problem of tail biting. Three equally big behavioral phenotypic groups, balanced for gender and age were selected, the data thus consisting of 11 trios of pigs. Two of the pigs in each trio originated from the same pen: one tail biter (TB) and one tail biting victim (V). A control (C) pig was selected from a pen without significant tail biting in the same farm room. We found an effect of tail biting behavioral phenotype on the metabolism of serotonin and dopamine, with a tendency for a higher 5-HIAA level in the prefrontal cortex (PFC) of TB compared to the other groups, while V pigs showed changes in both serotonin and dopamine metabolism in the striatum (ST) and limbic cortex (LC). Trp:BCAA and Trp:LNAA correlated positivelywith serotonin and 5-HIAA in the PFC, but only in TB pigs. Furthermore, in both ST and LC, several of the neurotransmitters and their metabolites correlated positively with the frequency of bites received by the pig. This is the first study indicating a link between brain neurotransmission and tail biting behavior in pigs with TB pigs showing a tendency for increased PFC serotonin metabolism and V pigs showing several changes in central dopamine and serotonin metabolism in their ST and LC, possibly due to the acute stress caused by being bitten.

Reference:  Valros, A., Palander, P., Heinonen, M., Munsterhjelm, C., Brunberg, E., Keeling, L., & Piepponen, P. (2015). Evidence for a link between tail biting and central monoamine metabolism in pigs (Sus scrofa domestica). Physiology & Behavior.

Pig tails