Anna Wallenbeck

Department of Environment and Animal Health, Swedish University of Agricultural Sciences (SLU)

Nils Lundeheim

Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences (SLU)

Rebecka Westin

Department of Environment and Animal Health, Swedish University of Agricultural Sciences (SLU) Gård&Djuhälsan, Sweden

Stefan Gunnarsson

Department of Environment and Animal Health, Swedish University of Agricultural Sciences (SLU)

Torun Wallgren

Department of Environment and Animal Health, Swedish University of Agricultural Sciences (SLU)

Caudophagy is a common problem associated with modern pig production and is an indicator of poor environmental conditions where the needs of pigs are not met.

Tail bites cause pain and can result in infections, leading to stunted growth and economic losses to the farm.


Typically, prevention of captive care has been based on tail docking during the first week of the piglet’s life. However, the European Directive 2008/120/EC prohibits routine tail docking as it considers that caudophagy can be prevented by improving the environment and management of pigs.

In Sweden, tail docking is prohibited and pigs are reared with intact tails. This article summarizes the experience of producers and practical solutions that could be implemented in other EU countries.


The challenge – intact tails without caution

Caudophagy is a frequent problem in intensive pig production, and it has been shown that it is a behavior related to poor environmental conditions in which pigs redirect their exploratory behavior towards manipulation and tail-biting of their congeners.

This redirected behavior adversely affects the health, productivity and animal welfare

Although tail docking has traditionally been used during the first week of life of piglets, performing this practice on a routine basis is no longer acceptable and is indicated in Directive 2008/120/EC, as it prevents tail biting but does not resolve the underlying cause.

Additionally, the fact that tail docking is usually done without analgesia results in acute and chronic pain.


The Swedish model

How the environment and practices such as environmental enrichment can reduce the incidence of caudophagyhas been studied for decades. However, only some EU countries, such as Sweden, actually breed pigs with intact tails.

1944: Sweden’s Animal Welfare Act of 1944 allowed tail docking, although this was a procedure that was willingly carried out.
1988: All surgical operations that could not be justified from a veterinary point of view were prohibited, including tail docking.
2018: This prohibition remains in force in the current Animal Welfare Act of 2018. The ban on tail docking is accompanied by other differences with respect to to other EU countries in terms of regulations affecting pig production in Sweden (Table 1).

Table 1. Compliance with management practices in the EU and Sweden under Directive 2008/120/EC

Swedish legislation requires more available space so that all pigs can lie down at the same time. In addition, it also contains measures such as providing enough space to ensure that all pigs can eat at the same time, avoiding competition for food.


The origin of caudophagy

Caudophagy is a multifactorial phenomenon influenced by various intrinsic and extrinsic factors.


It has been proven that caudophagy increases with age, and this fact can be related to the decrease in available space and, in the case of nulliparous sows, to the entry into heat (4-5 months) and the rejection of the males.


The sex of the animals influences the behavior of captivity in groups of pigs. Thus, several studies show that in mixed groups, males are more likely to be victims and females more likely to be biters.


Due to the sporadic nature of caudophagy, it is difficult to relate the genetic component of this behavior. Some studies suggest that there are racial differences, while others do not, and this discrepancy may be due to the size of the study sample, different breeds used in the studies, or differences in defining what is considered caudophagy.

However, a study of over 3,000 boars of the Swedish Landrace, Yorkshire and Hampshire breeds revealed that:

Landrace males: are more prone to caution
Yorkshire males: are victims of caudophagy more often
Hampshire males: they get bitten the least



In a study on heritability of caudophagic behavior, an unfavorable genetic correlation was found between caudophagy and the development of lean tissue and back fat thickness.

Taken together, the scientific evidence indicates that caudophagy may be influenced, to some extent, by genetic factors that may be negatively affected by selection in favor of increased lean tissue development.

 Housing Density 

EU legislation sets the housing density according to weight categories, while Swedish legislation states that the housing density for growing pigs should be based on the current weight of the pigs according to the formula:

0,17 + (Live Weight (kg)/130)

This implies that pigs bred under the EU minimum requirements have less space than those bred in Sweden and this difference becomes more noticeable around 80-110 kg PV, coinciding with the period of highest incidence of captivity.

According to the Swedish formula, 80 kg pigs should have 0,78 m2/pig space and 100 kg pigs should have 0,94 m2/pig space. In order to meet this requirement, the pigs are housed in pens of 0,8-0,9 m2/pig from the start of the fattening period.

Pigs from the same batch are sent for slaughter at different times: after approximately 60-70 days, one or two of the largest pigs in each pen are sent for slaughter. This process is repeated two or three times until the last pigs are sent for slaughter.

The extent to which housing density is modified to prevent caution is unknown, but with the increase in the number of piglets born and weaned from today’s hyperprolific sows, all available space is now in use. Therefore, reducing the stocking density will be difficult if producers are not willing to reduce the number of sows in production (fewer pigs per unit area) or to build new facilities (more space per pig).

 Group size 

There is a great variability of housing systems in the EU, but batch sizes are usually large (24 pigs/pen or more). In contrast, in Sweden pens for growing and fattening pigs usually house 10-13 animals.

Working with small groups has several benefits that could be key to raising pigs with intact tails:

A lower number of individuals/pen limits the number of potential victims in the event of an outbreak of caudophagy.

It facilitates to identify biting and chewing individuals, allowing the biter to be removed from the pen and treated or to separate the bitten pig.

It reduces the need to mix the piglets after weaning. This practice is stressful for the animals and promotes disease transmission, although it has not been clearly linked to caudophagy.


   Floor type 

Total slat floor is prohibited in Sweden, and 62-75% of the floor must be slat-free, while in the EU it is permitted to have total slat floors.

Compared to total slat floors, partial slat floors are better suited to the needs of pigs as they provide a more comfortable resting area.

Also, the type of floor largely determines the possibility of providing manipulable materials, such as straw, to stimulate the exploratory behavior of the pigs.

Slatted floors are designed to allow passage of urine and feces, which means that they are not suitable for providing manipulable material. In contrast, pens with a partial slatted floor or solid floor are compatible with the provision of manipulable material in the solid area.


  Air Quality 

Poor air quality has been identified as a risk factor for caudophagy.

An environment with high levels of harmful gases has been shown to be harmful to animal and human health, contributing to the development of respiratory diseases which, in turn, have been linked to the occurrence of episodes of caudophagy.

In Sweden, maximum limits for the different gases in pig facilities have been set to ensure good air quality and are different from those allowed in most Member States:

Ammonia < 10 ppm
Carbon dioxide < 3,000 ppm
Hydrogen sulphide < 0.5 ppm
Dust particles < 10 mg/m3

Animal Welfare inspectors are responsible for measuring the concentration of gases to ensure that legal requirements are met.


Council Directive 95/58/EC specifies that “housed animals shall not be kept in permanent darkness or without an appropriate period of rest from artificial light“, and natural lighting supported by artificial lighting (where necessary) shall be provided to meet physiological and ethological needs.

Swedish legislation stipulates that pig facilities (except for those in operation before 1989) must have windows and the pigs must be given natural and supplementary light appropriate to their daily rhythm and natural behavior (at least 40 lux – 8 hours a day).


 Slurry management 

The slurry management system is not directly related to the occurrence of caudophagy, but could be indirectly related to the possibility of giving an adequate amount of manipulable material to the pigs.

Swedish legislation recommends that maternity units should have slurry management systems adapted to receive large quantities of straw.

In this respect, a survey was carried out with Swedish producers on the frequency with which they have had blockages or other problems in their slurry management systems related to straw. Fifty-six per cent of producers in transition units and 81% of producers in bait units indicated that they had never had problems.

How do you avoid the straw jams?

Unlike other countries where a vacuum system is used to remove slurry, in Sweden only 13% of the transition units and 7% of the bait units use this system.

In the case of such systems, the pipe diameter must be at least 300 mm and the manure must be removed every 14 days.

To avoid blockages in the slats or along the slurry management system, chopped straw is normally used.



Council Directive 95/58/EC stipulates that animals must be fed a healthy and appropriate diet, in sufficient quantity and at regular intervals, with feeding and watering systems that minimize the risk of contamination.

In this respect, Swedish legislation states that feeders and drinkers must be dimensioned so that the animals can eat and drink “calmly and naturally”, which means that there must be sufficient drinking and feeding space to prevent aggression.

In addition, in the case of automatic feeding systems, pigs must be able to eat their daily ration within 12 hours.

In most Swedish fattening farms pigs eat ad libitum and when they reach 65 kg they receive restricted feeding, with a GMD of 474 g/day up to 30 kg and 946 g/day during the fattening period (30-120 kg).

Flaws in feed composition and defects in feeding systems have been identified as frequent causes of caudophagy in Swedish feedlots.

Some producers have pointed out that simply delaying the time of feeding can trigger an episode of caudophagy, which was confirmed in an epidemiological study that revealed that the probability of occurrence of caudophagy is 14 times higher in the case of farms with variable feeding schedules.

It has been shown that abnormal feeding and behavioral patterns can be used to predict outbreaks of caudophagy several weeks in advance.

The EFSA Animal Welfare expert group concluded that competition for food is one of the main predisposing factors for caudophagy.

Directive 2008/120/EC states that in the case of restricted group feeding, all pigs should have access to feed at the same time. In this respect, Swedish legislation specifies the trough space needed to ensure that this requirement is met.

Thus, in the case of growing pigs (30-130 kg), the minimum trough space is determined on the basis of the formula:

0.164 + (Body Weight (Kg PV)/538)





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