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.
The Tail Biting “WebHAT” (Web based Husbandry Advisory Tool) is a website designed to be an interactive resource providing information about the key risks for tail biting in pigs and practical suggestions to help reduce these risks on-farm.
Taking information from evidence-based sources and scientific literature, this WebHAT identifies a number of risks associated with tail biting (a key pig behaviour), and can be used to generate a report of prioritised, key tail-biting risks found on a farm and obtain suggestions to address the specific risks identified
Tail docking is a well-known practice in pig production, but it is also heavily criticised. An international team of researchers dived into the topic and wondered what its exact effects are on pigs – and what alternatives there are to avoid tail biting….
Note: This article is an approved summary of the Executive Summary which was published earlier this year at http://farewelldock.eu. In future issues of Pig Progress, to be published later this year, several participating researchers in this project will delve deeper into the individual topics they encountered.
Despite a long history of debate about negative affective states in animals, it was only in the last decades of the 20th century that the state of pain was mentioned in definitions of animal welfare, included in veterinary education, and became a target of scientific interest. Pain is a perceptional phenomenon built from information gathered by specialized sensory receptors for tissue damage and integrated into a discrete experience with a negative emotional valence in the brain. Based on knowledge about porcine neuroanatomy, physiology, and studies focusing on pig behavior and pathology, we review evidence for causes of pain in pigs, underlying biological mechanisms, as well as the possibility to quantify different types of indicators of pain states relevant to the welfare of the animals under production conditions. The presentation will primarily focus on pigs because of the dual purpose of this species as a meat producing as well as research animal species (the latter driven by the anatomical and physiological homologies with humans), making pigs unique among livestock. We will present methodologies and results from current research projects across Europe and North America targeting typical industry-related injuries (e.g., tail docking, lameness, and shoulder lesions) and aiming to understand the welfare consequences for the pigs. Throughout the talk, the emphasis will be put on future opportunities to link research outcomes with industry initiatives toward the improvement of animal welfare and production. In addition, possible future research efforts to help face current methodological limitations and favor a more comprehensive evaluation of animal pain as an overall experience will be discussed. This seeks to facilitate common future targeted research and enable us to overcome the paradoxical low level of knowledge about porcine pain and its alleviation under production conditions.
Tail docking of pigs is under scrutiny due to concerns about animal welfare. To reevaluate the consequences of raising pigs without tail docking under modern, commercial-like conditions, a study was conducted to compare welfare, behavior, and performance of pigs with and without tail docking. Pigs farrowed to 37 sows were used with half of each litter tail-docked (docked) after birth and remaining pigs left with tails intact (intact). During the nursery period, pigs (n = 336, initial wt = 7.8 ± 1.5 kg) were housed in 20 docked pens and 22 intact pens (8 pigs/pen). During the growing-finishing period, pigs (n = 240, initial wt = 24.9 ± 2.9 kg) were housed in 8 pens (4 pens each of docked and intact, 30 pigs/pen) for 16 wk (avg final wt = 126.2 ± 10.3 kg). Weight gain and feed intake were recorded. All pigs were assessed for tail damage and skin lesions every 4 wk and during outbreaks of tail biting. Behaviors were video-recorded twice weekly for 13 wk during the growing-finishing period. Carcass weights and incidence of carcass trim loss were recorded. More intact pigs experienced tail damage during both nursery (41% vs. 2%; chi-square = 75.7; P < 0.0001) and growing-finishing (89% vs. 48%; chi-square = 76.2; P < 0.0001) periods than docked pigs. Intact pigs spent more time tail biting (0.31% vs. 0.06%; P < 0.001) and tended to spend less time drinking (1.58 vs. 1.77%; P < 0.10) compared to docked pigs. Intact pigs experienced the first outbreak of tail biting at 11 wk of age, which occurred 6 wk earlier compared to docked pigs. Furthermore, 21% of intact pigs vs. 5% (P < 0.001) of docked pigs were removed due to tail damage. Tail docking did not affect ADG (nursery: 0.48 vs. 0.49 kg, SE = 0.04; growing-finishing: 0.86 vs. 0.87 kg, SE = 0.01 for docked and intact pigs, respectively) or skin lesions of pigs. For pigs that were not removed, ADFI was not different between pens with docked pigs and pens with intact pigs. As a consequence of carcass trim loss, carcass contamination, and mortality, 90% of intact pigs vs. 97% of docked pigs were harvested for full value. These data suggest that raising pigs without tail docking in a confinement housing system increases incidence of tail biting and tail damage, resulting in higher morbidity, reduced value, and compromised welfare of pigs.
Tail docking is an undesirable mutilation of pigs. Currently virtually all young piglets are docked in conventional farming so as to prevent tail biting later in life. However, throughout Europe efforts are made to reduce tail docking. Often farmers provide additional enrichment to try and prevent tail biting. Nevertheless, stopping the practice of tail docking may, and frequently does, lead to elevated levels of tail biting, resulting in tail wounds. In relation to this farmers and policy makers would like to know what levels of tail biting would be equivalent to tail docking in terms of pig welfare, i.e. how much tail biting can be allowed before deciding it would be better to continue tail docking. But this poses the problem how to weigh the (lack of) welfare involved in tail biting of a grower or finishing pig against the pain of tail docking of young piglets. Is this possible? And if so, how?
We recently had a brainstorm session on this subject. This is an outline of what we came up with, including a very tentative personal estimate (by MB).
In my personal view when (in the end up to) about 12% of undocked pigs were tail bitten that would be roughly equivalent in welfare to the docking of all piglets. The uncertainty margin, however, is high, at least ranging from 5-25%. The reasoning underlying my estimate is as follows.
Firstly, piglets are normally docked using hot iron cautery. This is quite painful as it involves applying both heat and rather blunt trauma. The heat kills bacteria and thus may reduce the chance of subsequent infection of the tail wound. Tail biting at a later age, by contrast, is caused by even more (and multiple) blunt trauma (due to biting). It also has a substantially higher likelihood of infection. In addition, there is e.g. fear in the tail bitten pig due to being chased by a biter. Based on this I would say that pain (and stress directly related to tail biting) may roughly be about ten times as high in intensity and about ten times as long in duration, compared to tail docking. This would imply that 1 tail-bitten pig is off-set by about 100 docked piglets as regards the intensity and duration of the pain involved.
However, animal welfare encompasses more than just pain. An important additional factor is the level of stress which is not directly related to tail biting activity.
Firstly, there may be stress related to the treatment of tail biting, e.g. when biters and/or victims are taken out of the pen (resulting in social isolation and/or fighting). This stressor, however, is partly offset by the enhanced enrichment normally provided to pigs experiencing an outbreak of tail biting (though not all pigs are equally affected by the ‘costs’ and ‘benefits’). Note that there is another, more macabre, offset involving ‘happiness’ too, and that is the excitement experienced by the (sometimes fanatic) biter pigs when a tail-biting outbreak has started. Note also, that this biter ‘welfare’ is at the same time an indicator of the level of (background) stress experienced by pigs leading to this abnormal behaviour in the first place.
A much more important source of stress that must be taken into account, therefore, is related to the general housing conditions to which the pigs are exposed prior to a tail biting outbreak. Tail biting is an unnatural behaviour that is triggered by (some kind of) stress. Pig farmers are aware of this and will try and prevent tail biting by generally improving the housing conditions when they (start to) raise pigs with intact (undocked) tails. Thus the expected level of stress to which the pigs are exposed is likely to be higher in the case of routine tail docking. When farmers stop tail docking they normally provide much better enrichment (rooting material & space). Farmers raising pigs with intact tails will also take other measures to reduce stress, e.g. provide better climatic conditions, better feed and better health care. These stress-reducing measures don’t just apply to the biters or the victims of tail biting. They apply to all pigs in the pen. Furthermore, they don’t just apply during an outbreak of tail biting, but they apply throughout the pigs’ lives. Hence, the reduced stress levels are a major factor reducing the off-set between docking and tail biting based exclusively on pain (and pain-related fear). I would estimate that the improved living conditions may reduce the off-set by at least a factor 10. This would mean that taking into account both pain and stress, 100(%) docked pigs (kept with minimal care and in a more barren environment) could be roughly equivalent to similarly-sized group of pigs with intact tails under enriched conditions and in which 10% of the pigs has been tail bitten.
Tail biting in docked pigs
However, we know that tail biting does not only occur in undocked pigs. It is also seen in docked pigs. Roughly 2% of docked pigs are tail bitten. It seems safe to assume that the level of pain from being tail bitten is roughly comparable in docked pigs and in undocked pigs (though docked tails may be more sensitive and thus less likely to get bitten). Taking this into account would imply that 100 docked pigs of which 2% also experiences tail biting later in life would be having a level of (poor) welfare comparable to 100 undocked pigs of which 12% gets tail bitten. This is about 6 times as much tail biting as the 2% base-line set under conventional docking conditions.
It must be emphasised again, however, that this level of 12% tail biting is a very rough estimate. So, a wide safety-margin applies, e.g. 5-25%. This may depend in particular on the quality of enrichment and the extra care provided under non-docking conditions.
Please note, that this post is the result of a brainstorm session only and presents a personal view. It illustrates how systematic reasoning (using principles of semantic modelling) can be used to start to answer this rather important welfare question. I have provided a very rough estimate. For a more accurate assessment more detailed studies would certainly be required, both in terms of more carefully including what is already known and in terms of accumulating more empirical knowledge about what is not known yet. At present the assessment is still very speculative, and meant to illustrate primarily how to in principle deal with the question of what level of tail biting is equivalent to a practice of routine tail docking.
Postscript: Excluded aspects and some feedback from readers
Note that, in my estimate I neglected several (minor) aspects.
Firstly, I neglected the fact that for tail docking piglets must be picked up. This results in stress, both in the mother sow and in the piglets. From an evolutionary perspective the procedure of catching piglets may be equivalent to experiencing capture by a predator. This would mean that the given estimate would be a moderate underestimation. However, tail docking may be performed in combination with other treatments such as iron injection and castration. If so, the additional stress from handling may be relatively minor. Note, however, that castration applies only to males and may be banned in the near future, and iron injection may be given orally as a kind of ingestible compost, or as has recently been shown, may not be necessary at all. Hence, combining such treatments with tail docking has a reducing likelihood.
Secondly, I assumed that teeth cutting will not be practiced to treat an outbreak of tail biting, neither in the docked pigs, nor in the undocked pigs. Or, more precisely, at least I assumed teeth cutting is not practiced in substantially different numbers of pig. Such teeth cutting is painful and illegal, so it could be considered appropriate to ignore the practice. However, if it were practiced more in undocked pigs (which are likely to experience higher levels of tail biting), then it would have a substantial impact on the level of equivalence, pushing the percentage back down again substantially.
A third point to note is that I did not include in the estimate other ethical considerations or our (anthropomorphic) emotional responses. An example of the latter may be related to the amount of blood seen in the pen, the farmer’s level of stress (unpredictability) associated to this, and the potentially adverse economic consequences associated with tail biting. An example of other ethical considerations is the fact that tail docking may be considered to be an infringement of the animals’ integrity or intrinsic value. In such a rights-based moral view tail docking may be considered ethically wrong, regardless of the level of tail biting when tail docking is stopped. Such aspects were excluded because these are aspects not directly related to animal welfare. They are more related to our human perception of ethics and/or human welfare, rather than animal welfare.
Finally, it is most important to emphasise that I have considered steady-state conditions, but realize that all practices are subject to optimisation. The practice of tail docking has already been optimised for over a period of at least 50 year. By contrast, the practice of raising pigs with intact tails still more or less has to enter the phase of optimisation in commercial practice. This implies that substantially higher levels of tail biting may be regarded as acceptable, provided this is only temporary and provided it leads to substantially lower levels of tail biting later on. In other words, it requires that farmers will persist in raising pigs with intact tails and have a chance to learn to deal with it over a certain transition period, both in terms of prevention and treatment of tail-biting outbreaks.
Feedback reader 1:
Regarding the painfulness of tail biting vs tail docking, I find it impossible to guess the relation – especially as tail biting comes in so many forms.
I absolutely agree that a weighing like this is necessary, but I also think it is a bit dangerous to throw out estimates that are not really based on any evidence (or at least you do not present any?), such as the 100 times worse pain experienced by bitten pigs than docked pigs. Also, tail biting is very heterogeneous, from just a small, one-time bite, to a chronic situation, where the entire tail is lost, so the way you estimate the pain simplifies the matter greatly.
As to the expected level of actual tail biting when docking is stopped: I estimate a two-fold increase in tail biting if no docking is performed. Perhaps somewhere between 2- and 4-fold, based on e.g. slaughterhouse data. There may be a 4-fold increase when the housing situation is not improved otherwise – which you also take into account in your text – when applying a non-docking policy the farmer would normally also improve housing conditions, thus reducing the risk further. I certainly agree that when a farm stops docking, they will probably have a higher incidence of tail biting initially, but on the long-term (as is shown e.g. in Finland where tail docking is totally forbidden, and the tail-biting incidence, based on abattoir data is around 2%), a 10 or 12% incidence is certainly higher than I would expect.
Feedback reader 2:
Having read your blog I think you need to factor in adaptive, compensatory pain modulation into your model.
It is sometimes too easy to fail to take into account post-injury peripheral and central modulation of pain signalling that occur as part of the normal healing process and only focus on the ‘pro-pain’ component.
I also don’t see how you can substantiate this claim?
‘Based on this I would say that the pain of tail biting may be about ten times as high and about ten times as long, compared to tail docking. This would imply that 1 tail-bitten pig is off-set by about 100 docked piglets as regards the intensity and duration of the pain involved’.
While I think it might be possible to attribute weighting to some risk factors within systems, I don’t think it can be applied to pain experienced by an individual (or even at group level as you are suggesting) because there are so many factors that contribute to an individual’s experience of pain? I don’t think you can quantify the painfulness of tail biting and tail docking.
Also when thinking about stress you might want to define what you mean by that in relation to chronicity?
Short-term compensatory responses to stress are in my view positive for the animal; however beyond that when there is a failure of compensation and ultimately homeostatic decompensation then they are undoubtedly negative.
I guess I’m suggesting that any weighting approach might need to accommodate (or factor in) changes over time (i.e. dynamic weighting?)
I hope you find my comments helpful?
As to substantiation, again, it’s my suggestion for a start of an argument to answer this in my view fairly important question. My answer is based on my personal experience as a vet and scientist, and on reasons indicated in the blog. It is certainly in need of further study, examination and assessment. I fully acknowledge the considerable level of uncertainty as well as the risk associated with trying to answer the question. At the same time, however, I would also argue that there is a considerable risk in refusing to try to answer the question, as this leaves the issue to stakeholders.
Feedback reader 3:
Joining the discussion rather late, but basically I agree with the points others have made. I think it quite reasonable to conceptually set out the trade-offs which would determine the level of tail biting above which tail docking could be ethically justified, but putting numbers on some of these things is rather difficult.
For risk of tail biting in docked and undocked pigs we have a growing number of published sources and comparative national data.
For experimental comparisons we have old data suggesting increases of 30-60% in pigs in unbedded systems.
More recently we have studies suggesting somewhat lower results if straw is given.
So this part is perhaps simple, but depends on your assumptions about which husbandry systems will pertain across Europe.
For the welfare detriment of tail docking and tail biting, data indicate that both have long lasting effects on pain processing pathways, but the implications of this for pain perception for the individual are uncertain.
For tail docking, the data I have seen are still contradictory on whether cautery is more or less painful than simple section (some suggest the cautery destroys the nerves whilst others suggest greater pain). There is also the possibility of tail docking with anaesthesia/analgesia as a route of adoption.
For tail biting, the short term pain will certainly depend on the severity and, even more, on the prevalence of infection. The data on this are currently lacking to my knowledge.
The welfare impairment of keeping in conditions which give rise to tail biting is clearly the greatest of all in magnitude (severity x duration x no of animals) but I don’t think we have any way of comparing the welfare severity of ‘behavioural frustration’ against that of injury/pain. I would be concerned about taking arbitrary figures in the absence of any logical basis.
So, I guess my suggestion would be to explore the framework for this decision, but be very wary about pretending we can quantify it.
I also think the issue not addressed in your blog is the time course of any transition to cessation of tail docking and how to manage this. What proportion of farmers would have the awareness, capital and staff training to implement the changes necessary to their existing housing if obliged to cease tail docking (some older, fully slatted and large group housing systems will pose much bigger challenges and possibly require replacement of buildings), and how long would it take across Europe to reach the ‘acceptable’ situation of relatively low differential in tail-biting prevalence between docked and intact tails, rather than the ‘unacceptable’ differential shown for “one off” change in tail-docking experiments (stopping docking without further improvement of the environmental conditions). I think it important to highlight that your analysis relates to a ‘steady state’ situation and the importance of how any transition is managed and the welfare implications which this will have.
Note that I have not been comparing docking versus non-docking in a mono-factorial way. I compared docking in a more barren environment versus not docking in a more enriched environment supplemented with special attention by the farmer, as that is what will normally happen in practice. I have now emphasised this more clearly in the text.
I largely agree that we currently largely lack the data needed to quantify more precisely. However, I also believe that in principle it is possible to do so, and that the estimate/assessment can be more or less verified empirically (as the body of knowledge accumulates and modelling principles are improved). Personally, I am inclined to try and quantify despite considerable uncertainty, because it provides a better starting point for further discussion. In addition, such preliminary but more science-based estimates are much needed to complement the inevitably politically-loaded figures and personal assessments presented by farmer-representatives and NGO’s arguing either (rather exclusively) against or in favour of ending tail docking as a routine practice to prevent tail biting.
An important point I’ve been trying to make is that pain is not the only relevant aspect of welfare involved in tail docking and tail biting, and that the levels of enrichment and care should also be taken into account. I don’t think it is even possible to honestly say it is not possible to ‘add’ these aspects, since proper political decision making (in all kinds of areas, not just tail biting) simply does and has to, whether it is considered scientifically possible or not. And if so, I would argue it is most reasonable to try and provide the best possible scientific support, while being as honest as possible e.g. about uncertainty margins and the relevance of incorporating more information. I also think the estimate provides broad support to ‘farewell-dock’ initiatives such as those in Finland, Sweden, Denmark, the Netherlands, the UK and Germany.
Report identifies good practices for rearing pigs with intact tails
DG Health and Food Safety – European Commission
A new report provides evidence that there are solutions to counter the commonly held belief that rearing pigs and avoiding tail docking is impossible.
Based on visits to three countries where tail docking is not performed routinely, it summarises good practices to rear pigs with intact tails. It finds that the key to do so is to lower stress levels through active management of enrichment materials; feed and air quality; reduction of competition between animals; and good animal health status. Another key factor to ensure intact tails is that farmers rapidly identify tail biters and remove them to prevent the escalation of tail biting.
The FareWellDock factsheets are out. Below you find the cover factsheet as well as the factsheets on tail docking, enrichment, health and the prediction of tail biting. This post shows images of the English versions, and links to the pdf version of the English factsheets, as well as all factsheets in Danish, Dutch, Finnish, French, Italian, Norwegian and Swedish. Separate pages are available directly showing the factsheets in the other languages (Danish, Dutch, Finnish, French, Italian, Norwegian and Swedish).
Please have a look at this pig’s tail. You may note that contrary to most EU pigs, this Finnish pig has a curly tail. In addition, please note that this pig does not only has a curly tail. Its tail also has a hairy plume. That is what a pig’s tail should look like: It is the pig’s welfare thermometer.
Curly tail as sign of melting pig-welfare iceberg
The FareWellDock project has accumulated scientific information directed at reducing the need for tail docking in Europe. In this way it has contributed to ending the progressive melting of the pig-welfare iceberg. But sometimes, a picture says more than a thousand words, for the pig’s tail is an iceberg indicator for pig welfare.
Background: Tail biting is a common problem in intensive pig farming, affecting both welfare and production. Although routine tail docking is banned within the EU, it remains a common practice to prevent tail biting. Straw as environmental enrichment has been proposed as an alternative to tail docking, but its effectiveness against tail biting and function in manure handling systems have to be considered. The aim of the study was to survey how pigs with intact tails are raised and how tail biting is handled in Sweden, where tail docking is banned through national legislation. The study emphasises straw usage and its association with tail biting pigs and problems in the manure handling system. The expectation is that this information could be conveyed to the rest of the EU to reduce the need for tail docking.
Results: In a telephone survey of randomly selected Swedish pig farmers (46 nursery and 43 finishing pig units) with at least 50 sows or 300 finishing places, it was found that straw was used by 98% of the farmers. The median daily straw ration provided was 29 g/pig for nursery and 50 g/pig for finishing pigs in systems with partly slatted flooring. The reported prevalence of tail biting was 1.6% at slaughter. The majority of farmers reported that they never had manure handling problems caused by straw (56% of nursery units and 81% of finishing pig units). A proportion of farmers (37%) also provided with additional material apart from straw on some occasions, which may have affected tail biting prevalence and manure handling problems.
Conclusions: Swedish farmers rear undocked pigs without large problems with tail biting. Straw is the main manipulable material used, and additional manipulable material is used to various extents. The low incidence of straw obstructing the manure handling systems implies that it is indeed possible to use straw in partly slatted flooring systems, reducing the need for tail docking. The impact of using additional manipulable material is unknown and requires more investigation to separate the impact of such material from the impact of straw.