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
Abstract
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.
Tail biting is a common and serious welfare problem in pig production, causing large economical losses. Tail docking is performed routinely in most EU countries to reduce the tail biting risk. However, tail docking is painful, and does not prevent tail biting totally. In Finland, tail docking is forbidden. New research shows that most Finnish producers would not raise tail docked pigs if it were possible.
Professor Anna Valros led a project asking with a web-survey from the Finnish farmers how they manage to raise pigs without tail docking. Respondents scored feeding-related issues to be most important for prevention of tail biting, identifying and removing the biting pig as most important intervention measures, and straw as the most important manipulable material when preventing tail biting. Tail biting was not perceived as a serious problem by over 70% of the respondents, even though docking is not allowed, and was reported to occur close to a level which was also considered acceptable by the respondents. Most respondents did not think it is probable they would raise tail docked pigs if it were possible, but about 21 % probably would.
These results are important for trying to reduce the risk of tail biting, and subsequently the need for tail docking on an international level.
This first week of February 2016 two items related to tail biting appeared in farmers’ press in The Netherlands. In addition, we recently provided input into a European project on the welfare of poultry, which will be reported on briefly below.
One news item announced that farmers are invited at the Intensive Farming Fair in Venray (LIV Venray), March 1-3 2016. At the fair two finished tail-biting projects will be presented and discussed with entrepreneurs who are active in intensive farming. One of the projects is ‘Keeping pigs with intact tails’.
The other item was a report on the German tail biting (Ringelschwanz-)project. First results of the curly-tail project in North-Rhine Westphalia showed that more than one quarter of piglets at 15 participating research farms had damaged tails before the end of the rearing period. At some farms half of the tails had been bitten. At the 15 farms participating in the study 30-94 piglets had been reared on each farm without tail docking. Outbreaks of tail biting appeared to be associated with streptococcus infections. Prevention and intervention strategies included providing dried maize silage or alfalfa hay twice daily and the isolation of biters respectively. Most tail biting occurred between week 2 and 4 after weaning. This level of tail biting is not so good news. If these levels of tail biting would persist, it may indicate that intensive systems cannot be made compatible with acceptable levels of animal welfare. Fortunately, however, experiences in Finland indicate that it should be possible to keep undocked pigs in conventional systems at much lower levels of tail biting (around 2% based on slaughter house data).
The German farmers union and North-Rhine Westphalia have agreed 1.5 years ago that they intend to stop tail docking by 2017. This will be done provided on-farm research shows that tail biting among pigs with intact tails does not reduce animal welfare. The general expectation is that the objective of safely quitting tail docking cannot be met.
From a Dutch research perspective two notes appear to be relevant:
The first is that our semantic-modelling approach provides a unique methodology to determine/assess the cut-off point between the welfare impacts of tail biting and tail docking using formalised biological reasoning and scientific evidence. In this computation one must take into account all relevant aspects: So, not only the point that the welfare of tail bitten pigs is reduced due to blunt trauma (biting) compared to the sharp trauma of tail docking at an earlier age. But also the point must be recognised that the welfare of tail biting pigs may relatively be improved when they can bite their penmates’ tails, compared to when they cannot (other things being equal, i.e. lack of suitable enrichment). What matters for welfare as considered from the animals’ point of view is the extent to which they can satisfy their needs, e.g. for biting and the expression of species-specific foraging behaviour, taking into account also the activation of coping mechanisms such as redirected and harmful-social behaviours.
The second thing to note about the results of the German research project is the following. In addition to taking note of the bad news (many bitten tails, which has to be taken seriously, perhaps even to the point that the conclusion must be drawn that intensive systems are not compatible with acceptable animal welfare), one may also try to move forwards for the time being by focussing on the good news: Two out of the 15 pilot farms in Germany managed to keep all piglets’ tails intact. Other farms may learn from what was done on these farms to keep tails intact. Furthermore, since the EC Directive requires that all farms try to periodically keep at least some intact pigs, a 10% success rate could provide sufficient scope for progress at the population level, even when the causes of the success are poorly understood. This can be concluded from a methodology we designed previously to solve complex welfare problems like feather pecking in poultry and tail biting in pigs. This methodology has been called ‘Intelligent Natural Design’ (INO in Dutch; see also Bracke, 2010). It basically uses evolution to select the best farms to make increasing progress towards the objective of completely stopping the practice of routine tail docking in pig farming.
Countering the routine practices of tail docking and beak trimming, as well as preventing and treating outbreaks of tail biting and feather pecking requires an understanding of tipping points. Recently, we modified our tipping-bucket model for tail biting for inclusion on the Henhub website. This website, which is part of the Hennovation project, gives information about welfare issues in poultry, esp. (at present) feather pecking. On that site the modified tipping-bucket model can be found under the post describing the mechanism of feather pecking.
Tipping-bucket model of tail biting in pigs
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Bracke, M.B.M. 2010. Towards long(er) pig tails: New strategy to solve animal welfare problems. In: Lidfors, L., Blokhuis, H., Keeling, L., Proceedings of the 44th Congress of the ISAE, August 4-7 2010, Wageningen Academic Publishers, Wageningen, p. 135. (Poster, ISAE 2010, Uppsala, Sweden, Aug 4-7.
A 4-year project of “Strategies to reduce the risk of tail biting in pigs managed on slatted floors” has started. It is a collaboration between Teagasc, SRUC and the University of Edinburgh.
Below is a poster on the project presented in the Teagasc Pig Farmers’ Conference 2015.
The project will aim to explore ways to reduce tail-biting on slatted floor systems where straw is not available by environmental enrichment and nutritional strategies.
The enrichments used at the moment are compressed straw and different wood types.
Later the project will also investigate the effects of various lengths of tails, measures to predict tail-biting outbreaks and methods to interfere effectively.
The project will be supervised by Dr Keelin O’Driscoll (Teagasc), Dr Rick D’Eath (SRUC), Dr Dale Sandercock (SRUC), and Prof Natalie Waran (University of Edinburgh).
Dr Amy Haigh is the postdoctoral researcher working together on this project in Teagasc, and Dr Laura Boyle and Dr Edgar Garcia Manzanilla are also the collaborating researchers in Teagasc. I (Jen-Yun) am the PhD student on this project.
Description are provided by the Actions directly via e-COST.
The GroupHouseNet aim is to provide the European livestock industry with innovations in breeding and management for pigs and poultry that are needed for a successful transition to large group housing systems without necessitating painful tail docking and beak trimming. Allowing the animals greater opportunities to display their species-specific behaviour while avoiding the routine use of painful procedures, group housing of unmutilated animals sits at the core of the new animal welfare paradigm driven by consumer demand. Group housing is associated with increased risks of damaging behaviours among the animals, such as feather pecking, aggression and cannibalism in laying hens and tail biting, bellynosing, excessive aggression and cannibalism in pigs. Recent research suggests the key to reducing the incidence of these behaviours lies in refining and applying methods of genetic selection, and developing husbandry innovations that improve early and later life conditions – which is exactly what GroupHouseNet will use the COST Action framework and tools to do. GroupHouseNet brings together researchers and industrial partners dealing with animal breeding and genetics, animal nutrition, epidemiology, engineering, animal behaviour and welfare, epigenetics, immunology, (neuro)physiology, economics and ethics. To strengthen the scientific and technological basis in these areas the Action will facilitate knowledge sharing, creation and application in pigs and laying hens in both experimental and commercial environments. The activities will be conducted in an open, output-oriented transnational, multisectorial, and multidisciplinary research and development network emphasising COST Excellence and Inclusiveness Policy.
Proposer of the action: Prof Andrew Janczak
(action arising in part from the FareWellDock project).
As a follow-up to the German tail biting research review, German federal research institutions are currently making arrangements for better cooperation and coordination of their tail biting research. Representatives agreed to update an existing lesion scoring format from 2011 in such a way that it can be used to score tail and ear lesions in basic research as well as on-farm projects. In addition, a web-based database for tail biting experiments and projects will be launched in 2016 in order to facilitate knowledge exchange. The database will be based at the Institute of Animal Welfare and Animal Husbandry (ITT) within the German Federal Research Institute for Animal Health (FLI).
We investigated the effect of straw amount on pigs’ time spent manipulating straw.
We investigated the effect of straw amount on pigs’ simultaneous straw manipulation.
Increasing straw from 10 to 430 g/pig/day increased both measures.
Increasing straw above approx. 250 g did not significantly increase the behaviour further.
Abstract
According to European legislation, pigs must have permanent access to sufficient quantity of material to enable manipulation activities. However, few studies have quantified how much straw is needed to fulfil the requirements of growing pigs. We investigated the effect of increasing amount of straw on pigs’ manipulation of the straw, and hypothesised that after a certain point increasing straw amount will no longer increase oral manipulation further. From 30 to 80 kg live weight, pigs were housed in 90 groups of 18 pigs in pens (5.48 m × 2.48 m) with partly slatted concrete floor and daily provided with fresh uncut straw onto the solid part of the floor. Experimental treatments were 10, 80, 150, 220, 290, 360, 430 or 500 g straw per pig and day. At 40 and 80 kg live weight, the time spent in oral manipulation of the straw by three focal pigs per pen (large, medium and small sized) were recorded along with the percentage of pigs manipulating straw simultaneously. This was recorded in three 1-h intervals (1 h before and 1 h after straw allocation in the morning, as well as from 17 to 18 h in the afternoon). With increasing quantity of straw provided, we found a curvilinear (P < 0.01) increase in the time spent in oral manipulation of the straw. Smaller pigs spent more time manipulating straw than larger and medium sized pigs (367, 274 and 252 s/h for small, medium and large sized pigs, respectively; P < 0.001), and pigs spent more time manipulating straw at 40 kg than 80 kg live weight (356 vs. 250 s/h; P < 0.001). At both live weights, pigs spent most time manipulating straw during the hour after allocation of straw. Similar effects of increasing amounts of straw were found for the percentage of pigs engaged in simultaneous manipulation of the straw. Post hoc analyses were applied to estimate the point, after which additional straw did not increase manipulation of straw any further. For the time spent manipulating straw the estimated change point was 253 (approx. 95% confidence limits (CL) 148–358) g straw per pig and day. For the number of pigs simultaneously manipulating straw the change point was 248 (CL 191–304) g straw per pig and day. These results show that increasing the quantity of straw from minimal to approximately 250 g per pig and day increased the time spent in oral manipulation of the straw, as well as the occurrence of simultaneous straw manipulation.
Hence, data from the current experiment identified 250 g straw per pig per day as the amount of straw where a further increase in straw provision did not further increase neither time spent on oral manipulation of straw, nor the percentage of pigs simultaneously manipulating straw. This suggests that, within the current housing system and using this criterion, this amount of straw may be the biological turning point for increasing oral manipulation of straw.
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.
Summary
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.
Abstract
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.
Di Gininiani P, Stausholm JS, Viitasaari E, Petersen LJ, Herskin MS 2015. Description of mechanical nociceptive testing on hind legs and tails of pigs. Abstract 1054, Proceedings of the 9th EFIC Congress, Vienna, Sept 2-5.
The German Federal Research Institute for Animal Health (FLI) has reviewed current research on tail biting in pigs.
The report entitled “Übersicht über Untersuchungen zum Themenkomplex „Schwanzbeißen” makes specific recommendations as to how to best tackle the tail biting problem. The report also has an extensive appendix (under ‘documents’) listing projects, main project results and references on tail biting.
Twenty-six different research projects were counted in Germany alone. Many other projects were also listed in other EU countries (The Netherlands, Belgium, UK, Ireland, Denmark, Finland, Sweden, Norway, Spain and Hungary). Also the EFSA and FareWellDock activities were noted, as well as the International Pig Welfare Conference in Denmark in April 2015 (see our Soundbite posts 1, 2, 3, 4 and 5).
The report has a detailed list of recommendations split for the farm and regional level. At farm level risk assessment, gradual reduction of tail docking, networking, demonstration farms, and trying-out of practical solutions to prevent and treat tail biting are mentioned. At the regional and national level the report mentions the collection and distribution of knowledge in various ways, the coordination of activities, the building of networks of tail biting experts, education/training, the installation of an information platform and the support of research projects using standardised protocol and cooperation with other EU countries.
The report noted a trend for tail biting to start at rather earlier ages (shortly after weaning, but also even before weaning, as has previously been observed by Dr. Ursinus).
It was also noted that on average 70% of the pigs used in the 26 research and field projects in Germany had severe tail lesions. Since these projects were focussing on (improvements of) current housing conditions, it may be questioned whether and to what extent current systems are suited to finally succeed in stopping completely the current practice of tail docking.
