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Successfully Eliminate Tail Biting in Pigs to Improve Herd Performance

Across the world, each pig farm differs in its approach to tail docking. There are some units with consistent success in keeping pigs with long tails. Others are keen to continue docking to reduce problems with tail biting. Legislation was passed in 1994 banning tail docking in Europe. Increasing enforcement of the legislation means adopting new strategies to ensure compliance. Summary of remarks made by Nicole Kemper Prof. Dr. med. Vet., Director of the Institute for Animal Hygiene, Animal Welfare and Farm Animal Behavior, Veterinary University of Hannover, Germany.

Nicole Kemper

In Brief

● Tail biting is a common problem in pig herds, resulting in lesions that may decrease the value of the animal at slaughter.
● Tail docking as a routine procedure to reduce tail biting has been banned in Europe because it only masks the problem instead of addressing the cause.
● Long-term success raising pigs with long tails is achievable as long as care is taken to provide the right conditions for the animals.

Source: BIOMIN

Is keeping pigs with long tails possible?

This is an important question on many pig producers’ lips. Tail docking was a routine practice on most pig farms across Europe before legislation in 1994 made it illegal. Yet, there are still many European pig farms docking tails today. Stricter enforcement of the legislation is pushing producers to try keeping pigs with long tails. Consumers, retailers, and welfare organizations all have rising levels of interest in such issues. This is especially true for retailers who are increasing the number of undocked pigs in their programs.

Tail-docking is an effective way of minimizing the risk of tail biting, but understanding how to keep pigs with long tails is becoming increasingly important. This understanding should include how to keep pigs with long tails in existing systems. What are the prerequisites for managing pigs with long tails until slaughter? And is it possible to have continuous rather than intermittent success?

Keeping long tails brings benefits

In some situations, keeping pigs with long tails is not possible. Yet, the benefits of improving extrinsic and sanitary conditions on farm delivers a boost to production performance. If you can keep pigs with long tails, that is a key sign that you can achieve high management standards.

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Tail biting is multifactorial

There are a wide range of factors which cause tail biting. The scientific literature lists many factors related to tail biting, corresponding to a multitude of known triggers. Unfortunately, this means there is no clear-cut answer to keeping pigs with long tails. A more successful attitude is acknowledging tail lesions as an indicator that something has gone wrong.

This is true for both docked and undocked pigs. Long before tail lesions appear, there would have been a trigger, or series of triggers resulting in the tail biting behavior. The prevention of tail biting therefore needs to start long before the physical biting occurs. Although lesions are more obvious in undocked animals, they remain an indicator in both groups.

Tail docking masks the problems

In Europe, tails are still docked on most pig farms. But even in pigs with docked tails, the number of lesions is considerable. In a study conducted in a slaughterhouse with 5,500 pigs, tail lesions were found in 1% of all slaughtered animals using an automatic detection system. This figure is commonly supported in the scientific literature. The main reason for docking tails is to prevent tail biting but instead it masks the problem (DG Santé, 2016). Docking reduces the visible signs of tail biting, but it does not eliminate the underlying problems that cause tail biting behavior in the first place (Sutherland and Tucker, 2011).

Docking reduces the visible signs of tail biting, but it does not eliminate the underlying problems that cause tail biting in the first place

Extrinsic causes of tail biting

The extrinsic causes of tail biting, those coming from outside the pig, include:

  • Feed
  • Water
  • Housing conditions
  • Sanitary challenges (pen hygiene, pathogen load)
  • Structure of the pen
  • Pen mates

In most husbandry systems, pigs are kept in a low stimulus environment with little or no enrichment material.

Investigation, not aggression

Every pig has an intrinsic urge for investigatory and foraging behavior. But in an environment with little or no opportunity to exert this behavior, they have to find something else to explore, typically their pen mates. Tail biting is not an act of aggression, but an act of exploration and investigation.

Figure 1 shows the threshold levels for intrinsic urges (blue line) and extrinsic factors (red line) in pigs. Controlling the intrinsic threshold level of individual pigs is not possible, but everything should be done to keep the extrinsic threshold as high as possible so as not to trigger tail biting behavior.

Figure 1. Threshold levels in pigs | Source: BIOMIN
Figure 1. Threshold levels in pigs. Going above these tolerance threshold levels will result in tail biting behavior.
Source: BIOMIN

Tail biting over time

Tail biting is more likely to occur at certain times during the production cycle. This may differ between countries or management systems. Using a typical German four-week lactation system as an example, the most sensitive period for tail biting is around the second week in the rearing unit. In systems with longer lactation periods, the most sensitive period might be delayed until the fattening unit. Providing a good start for the pigs is key given that there are several factors in the lactation period that might influence tail biting at a later stage.

Implementing best practice at all stages

The aim of keeping pigs with long tails is to ensure they still have long tails at slaughter and that the tail has not been lost through biting. This involves implementing best practice in all areas at all stages of the cycle.

Tail biting is more likely to occur at certain times during the production cycle

Focus on housing

Raising pigs on fully slatted housing systems is very common in intensive pig units in Germany. Even in these systems, space and structure should be provided. Overcrowding and competition for space should be avoided. The structure of the pen should be enhanced to allow the pigs to use different areas for different behaviors. This might include areas with different climates, or providing separate areas for lying, feeding, playing, and performing elimination behavior.

Figure 2 shows a pen with an elevated section which increases the total floor space available for the animals, but also provides an area specifically for enrichment materials. Including a raised section in the pen is a good way of expanding space in existing systems.

Figure 2. Pen with elevated floor | Source: Kemper, 2020
Figure 2. Pen with elevated floor to increase space and provide an area specifically for investigatory behavior
Source: Kemper, 2020

Pen structure

In some countries, there are certain requirements for the structure of the pen which must be adhered to. In the Netherlands for example, 40% of floor space must be closed. The situation is very different in Germany where pigs are raised on fully slatted floor systems. Whatever the type of floor, space must be optimized by adding separating walls or providing appropriate enrichment materials that suit the particular situation on the farm.

The type of material used to build the pen should also be considered. Plastic slats should be avoided as they are louder than a slatted floor made from concrete and noise levels have been linked to tail biting behavior.

The importance of enrichment

Providing enrichment material for the pigs is of utmost importance. Enrichment materials are typically inorganic and include items such as chains. No matter what the enrichment material is, the pigs must be able to perform their natural rooting and exploratory behaviors.

In Europe, there is demand for pigs to have permanent access to organic materials such as hay or straw (EC Council Directive 2008/120/EC). This type of material can be supplied in small quantities on a daily basis as long as it is sufficient, appropriate and free from health risks. Ideally the material should be destructible and manipulable (D’Eath et al., 2014).

Risk-free enrichment material

Organic materials need to be checked for any factors that could be detrimental to health. This is because pigs will typically eat any organic material they are given. In fully slatted floor systems, the material may fall through the gaps in the floor and cause blockages in the slurry system. Therefore, organic enrichment material must be carefully selected and prepared or cut to an appropriate size. Where possible, the floor should be partly solid, or rubber mats could be used.

Enrichment material should be changed regularly. The material should not be stored in the compartment directly opposite the pigs so as not to take on the same smell. Enrichment material can be used as an early intervention tool to prevent larger outbreaks of tail biting (Lahrmann et al., 2018).

Organic enrichment materials, typically eaten by the pigs, need to be checked for any health risk factors such as mycotoxins

Examples of enrichment materials

Chopped straw is a good enrichment material, as is alfalfa pellets or hay. Peat is also used, especially for piglets, but Mycobacterium avium has been detected in peat which poses a hygiene risk.

Corn and corn products can be used as enrichment materials, but mycotoxin contamination of swine feed materials must be considered. Wagner et al. (2018) investigated mycotoxin contamination in various materials. They found high levels of deoxynivalenol (DON) and zearalenone (ZEN) in corn pellets and in corn silage (Table 1).

Table 1. Results of mycotoxin analysis via HPLC-MS/MS (µg/kg) corrected to 88% dry matter | Source: Wagner et al., 2018
Wood granulate< limit of detection< limit of detection
Flax straw497.4429.89
Alfalfa hay14.790.42
Rye straw meal196.17< limit of detection
Corn pellets5,053.651,219.87
Peat< limit of detection< limit of detection
Lignocellulose2.34< limit of detection
Hay pellets< limit of detection< limit of detection
Wheat straw132.3431.82
Corn silage1,673.36200.65

The source of the enrichment material should also be considered, especially during times when African Swine Fever is rife. Changing climates will affect the availability of materials such as hay, so farmers may look to alternative sources. This is not recommended because enrichment materials might carry pathogens into the animal husbandry system.

Extrinsic factors

Many climatic factors can trigger tail biting. Offering access to outdoor space where possible is nice, but the hygiene and animal health risks should be carefully considered. Figure 3 shows pigs with access to a comfortable but limited outside space where the risks are kept as low as possible.

Draughts, direct sunlight and extremes of temperature in the pen should be avoided. Figure 4 shows a photograph (a) and thermal image (b) of a unit in direct sunlight. The temperature of the pigs in direct sunlight exceeds the desired maximum level which could trigger tail biting behavior. Using a thermal imaging camera is a good way to detect areas of extreme heat or cold. If animals are huddled together, this is a sign of the temperature being too low.

Figure 3. Pigs with access to an outdoor space | Source: Kemper, 2020
Figure 3. Pigs with access to an outdoor space
Source: Kemper, 2020
Figure 4a and b. Photograph (a) and thermal image (b) of a pig pen in direct sunlight. | Source: Lechner, 2020
Figure 4a and b. Photograph (a) and thermal image (b) of a pig pen in direct sunlight.
Source: Lechner, 2020
Climatic conditions can trigger tail biting so the pen should be free from draughts, out of direct sunlight and kept at a moderate temperature

Air quality and general pen cleanliness should also be considered. In slatted floor systems, ammonia levels should be monitored and managed so that they do not exceed maximum levels.

Access to feed and water is essential. Each pig should be able to access feed and water without competition. The quality of both inputs should be maintained at a high level with no abrupt changes to the diet type or water source. Feed formulations should be adjusted to the nutritional requirements of the animals depending on their lifecycle stage. The diet should contain at least 4% fiber and adequate levels of minerals and amino acids. Feed and water should also be free from any toxins because toxins may also provoke tail biting.

Mycotoxins provoke tail biting

Mycotoxins are a contributing factor to tail biting behavior. Mycotoxin mitigation in the feed can be achieved by adding a mycotoxin binder product. Because of this, most pig producers include a mycotoxin binder product in their formulations as standard.

Mycotoxin mitigation products are commonly added to pig diets to remove the risk of mycotoxin contamination resulting in tail biting

Water quality and quantity is often overlooked in pig units. Less than 7% of pig rearing units use the correct flow rate (Pütz, 2014). Often it is too low or too high. The animal: drinker ratio may be incorrect (vom Brocke, 2014). The water flow rate should be adjusted according to the requirements at each lifecycle stage and the optimum animal: drinker ratio is 10:1.

Detecting mycotoxins

The best method for detecting the presence of mycotoxins in feed is by using specialized laboratories which carry out HPLC or mass spectrometry analysis techniques. BIOMIN offers support to customers wanting to test their feed for mycotoxin. Please contact your local representative for more information.

The human factor

Hygiene standards, especially with the prevalence of African Swine Fever, should be a top priority. All known biosecurity factors and pest control measures should be considered to prevent the infection and spread of diseases.

Over time, the importance of the human factor has been realized. The people looking after the pigs play a vital role in the success of keeping pigs with long tails. The best staff will regularly check animals for early signs of tail biting behavior which can be stopped before an outbreak occurs. As shown by Büttner et al. (2018), intensified levels of human-animal interaction can decrease tail biting behavior. The eye of the farmer is thus a vital tool in preventing tail biting.

Observing the animals daily and identifying the victims as well as the tail biters is key to success

Intrinsic factors

Animal health is a key component for success in pig herds with long tails. If the health status of the herd drops, the likelihood for success of keeping pigs with long tails is diminished. Munsterhjelm et al. (2019) showed that a controlled immune stimulation with lipopolysaccharides increased tail and ear directed behavior two days later. This highlights the importance of minimizing or eliminating any bacterial infections on the farm. To assist this, piglets must be purchased without any predisposition to infection and the necessary hygiene and batch management procedures must be in place.

Vaccinations have been shown to reduce the risk of tail and ear biting significantly so they must be administered correctly. If animals become sick or are the victims of tail biting, the provision of sufficient hospital pens is vital to prevent further spread throughout the rest of the herd.

Social interactions

Allowing social interactions between pigs is vital to reduce competition. There are many ways to achieve this, but the recommendation is to keep litters together and avoid mixing animals, especially those of different sizes. Combining three litters into one group is acceptable if the animals are similar in size.

In terms of genetics, there is no scientific evidence to suggest any differences between breeds or lines. Yet practical experience indicates that there are differences between individual animals. Factors including stress and toxins can lead to different locomotory and investigatory behavior patterns.

Early warning signs

Tail position provides an early warning sign of tail biting. If tails are hanging down (Wallgren et al., 2019) and tucked between the legs, this indicates that a tail biting outbreak might occur. When pigs are in a good condition their tails are curled (Figure 5). Tail position is only available as an indicator in undocked pigs, but other visual indicators such as belly nosing or an urgent need to explore orally are also indicators that something is wrong. Ear lesions and tail lesions are linked, so where ear lesions are present in docked animals, this suggests that tail biting would also be a problem.

Figure 5. Curled tails of pigs in good condition | Source: Kemper, 2020
Figure 5. Curled tails of pigs in good condition
Source: Kemper, 2020

As soon as the early warning signs are spotted, an emergency plan to separate and treat the affected pigs should be implemented. The affected pigs should be treated for pain and inflammation, and a visit from the vet may be needed in extreme cases. Where possible, the biter(s) should be identified and separated to assess what might be wrong. Adjustments can then be made to any resources or materials to eliminate the tail biting behavior.

Developments in technology are helping detect early warning signs. Tail position, grouping patterns of the animals, and levels of animal activity can all be monitored and analyzed. Emerging technologies will greatly assist the management of tail biting in the future.

New technologies aim to identify the early warning signs of tail biting

Continuous success

Even farms with very high standards and previous success of keeping pigs with long tails will still experience outbreaks of tail biting. This should not deter farmers, but it highlights the need for support from the whole team including the veterinarian and the nutritionist.

The farmers, veterinarians and pigs all have to be fit for purpose to achieve success. Best practices should be implemented on farm in terms of health, housing and management. The process of keeping pigs with long tails is a slow, gradual transition rather than an overnight solution. Farmers are encouraged to start with one pen or one department and expand from there.

Role of the veterinarian

The veterinarian has a vital role to play in the process. As well as issuing permission to use tail-docking in cases of documented needs, the veterinarian should offer support to the farmers at each step of the process to keeping pigs with long tails. Based on experience, the transition can take up to two years (Figures 6a and b).

Figure 6a. Photograph of herd before consultation started – tails docked. | Source: Lechner, 2020
Figure 6a. Photograph of herd before consultation started – tails docked.
Source: Lechner, 2020
Figure 6b. Photograph of herd 2.5 years later after consultation – tails long and curled | Source: Lechner, 2020
Figure 6b. Photograph of herd 2.5 years later after consultation – tails long and curled
Source: Lechner, 2020
Keeping pigs with long tails is possible, but it is not easy. There are high demands, but the necessary actions are beneficial for production

Quantifying success

Putting a figure on the additional revenue from pigs with long tails is extremely complex and needs to happen at individual farm level. Pastorelli et al. (2012) tried to quantify the impact of sanitary challenges on weight gain, performance and growth. They found that a lipopolysaccharide challenge accounted for 30% of losses. The most important factor was bacterial digestive diseases which accounted for 40% of total reductions, but also sanitary deficits had a high impact. All these factors are related to tail biting so there could be a significant impact on performance, both zootechnical and economical.

One bitten tail is one too many

There is no room for tolerance of any incidents of tail biting on commercial pig units. As soon as one pig is bitten, action needs to be taken. In studies at slaughterhouses around the world where the majority of pigs passing through are docked, anywhere from 1% to 5% of tails show lesions as a result of tail biting. On closer inspection of different batches arriving to the slaughterhouse, large variation is seen. Some batches have zero cases of tail biting whereas others show up to 80% tail biting. The number of tail biting lesions detected at the slaughterhouse are typically lower than the number of lesions found in living pigs. This is because minor lesions are often missed by the automatic scoring systems used at the slaughterhouse. Therefore, the global estimate should be considered as low.

As soon as one pig is bitten, action needs to be taken

A zero tolerance to tail biting cannot be maintained in every situation, but nor can culling 80% of the herd. A more reasonable approach would be to track batches from the same farm over a period e.g. a year. A suitable benchmark can then be set for that farm, but these levels are still a big discussion point.

Belly nosing not a precursor

Belly nosing is not an aggressive behavior, nor is it related to defining hierarchy among the group. Belly nosing is an exploratory behavior often seen in piglets weaned very early, or those raised by artificial nursing systems as opposed to the mother. It can be taken as a sign that the pigs were not able to fulfil their needs for contact with others, especially the mother.

If there are concerns that belly nosing is becoming a problem, the target body part should be identified. If the pigs are attacking the head, the front, or the shoulders of the counterpart, this is aggressive behavior. Exploratory behavior is targeted at the softer parts of the animal such as the ears and stomach. This also includes the tail which is an interesting body part for pigs.

Can diet help?

The diet provided to the animals must always be optimized to the specific nutritional requirements based on lifecycle stage. The enrichment material can provide an excellent additional source of fiber, supporting gut function. Straw is highly recommended as an enrichment material, as is alfalfa.

Risk factors during lactation

Outbreaks of tail biting can also occur in newborn piglets. The biggest risk factors arise in uneven litters, where there is a big difference between the largest and the smallest animals. High management standards, especially during the lactation period is a good prevention tool. Cross-fostering can be used to ensure litters are all a similar size.

Another factor to consider during lactation is the sow feed. If the sow feed is contaminated with a high level of mycotoxins, this may also be contaminating the piglets. Ergot alkaloids have been identified as one mycotoxin with links to tail biting behavior, but this extends to all mycotoxins which affect the blood system. Most of the research focuses on DON and ZEA as well as ergot alkaloids. Other mycotoxins might also trigger tail biting behavior, but they have not yet been considered in the scientific literature.


Keeping pigs with long tails is possible under the correct circumstances. Every intrinsic and external factor that could contribute to an outbreak of tail biting behavior should be examined and constantly monitored. Emerging technologies aim to help farmers achieve success in raising pigs with long tails, especially as stricter enforcements are implemented in Europe.



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Effects of an intensified human-animal interaction on tail biting in pigs during the rearing period. The Journal of Agricultural Science. 156(8). 1-8.

D’Eath, R.B., Arnott, G., Turner, S.P., Jensen, T., Lahrmann, H.P., Busch, M.E., Niemi. J.K., Lawrence, A. and Sandøe, P. (2014).

Injurious tail biting in pigs: How can it be controlled in existing systems without tail docking? Animal. 8(9).

DG Sante. (2016).

Official Journal of the European Union L62. Commission recommendation (EU) 2016/336. Volume 59. 9 March 2016.

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Keeping pigs with long tails – is it possible? [Webinar]. Available at: p (Accessed: 25 July 2020).

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Meta-analysis of feed intake and growth responses of growing pigs after a sanitary challenge. Animal. 6(6). 952-961.

Pütz, S. (2014).

‘Development and validation of practical measures to avoid routine tail docking in pigs in conventional fattening.’ Masters thesis, Georg-August University of Göttingen, Göttingen.

Sutherland, M.A. and Tucker, C.B. (2011).

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vom Brocke, A.L.L.E. (2014).

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Wagner, K.M., Schulz, J. and Kemper, N. (2018).

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Prof. Dr. med. Vet. Nicole Kemper
Director of the Institute for Animal Hygiene, Animal Welfare and Farm Animal Behavior, Veterinary University of Hannover, Germany