Throughout its evolution, the pig has developed and passed on genetically fixed behavioural patterns that evolved as part of adaptation to their natural habitat. Modern pig breeds still carry these behavioural patterns. Pigs live in small groups in the wild and spend the majority of their days foraging – nosing, rooting, chewing tree bark – with a variety of environmental stimuli to keep them occupied. These stimuli are not present in modern pig production systems, while the pig still has the behavioural need to forage. Animals reared under such unstimulating conditions will develop stress sooner or later.
Stress leads to a reduction in feed intake and poor immune response, which negatively affects profitability and the general health status of the herd. This causes an increase in medication costs, mortality rates and feed conversion ratio. These factors will increase the input costs of pig production, which negatively affects productivity.
As a consequence of large scale animal farming, natural elements providing enrichment have almost disappeared from the pigs’ environment-in particular in pig breeding and fattening systems. The animals have become more stressed in this “foreign” environment. We have also switched from lard-type pig breeds to meat breeds with a higher meat producing capacity that tolerate stress poorly. It has to be noted that today breeding organisations/genetic companies put great emphasis on eliminating genetic lines prone to stress and developing more productive breeds capable of producing better quality meat.
Various stress factors affecting tail biting:
Despite our best efforts, the animals are subject to management related stress factors that negatively affect their well-being. Such factors include low-stimulus environments, overstocking, inadequate access to feed, restricted access to water, floor quality, air quality, temperature and humidity issues, heat stress and draughts. The negative effects of the above factors are exacerbated by the animals becoming more susceptible to various pathogens and diseases as a result of the increased stress levels, while stress may also lead to tail biting.
These stress factors may be present in all age groups depending on the management technology but special attention must be paid to mitigate these stressors in high value breeding animals. Gilt development and nutrition requires precise management as they will become replacement animals in the breeding herd. The most important area to consider is stocking density. The optimal space an animal between 50-100 kg bodyweight needs is 1.0 m²/animal, while for animals above 100 kg bodyweight it is 1.5-2.0 m²/animal. Appropriate nutrition poses a special challenge when rearing breeding gilts as daily weight gains should be limited to maintain a long useful life. This can be achieved by providing special gilt feed that is rich in fibre and less concentrated. This allows the appropriate filling of the gastrointestinal tract and lowers the risk of aggression caused by hunger.
Consequences:
The above mentioned stress factors can lead to behavioural problems that require time and money consuming interventions while also negatively affecting production results. Tail biting is such a behavioural problem that involves “biters” chewing the tails of the “bitten” animals. This may reach such an extent that the tail of the bitten animal becomes an open wound, providing an opportunity to pathogens to invade the body. An infection of the wound and continuous biting may result in the tail disappearing, leaving only a large open wound. The bitten pigs may succumb to diseases easily during fattening, show reduced gain, decrease their feed intake, become unfit for marketing or even die.
Source: Magyar Állatorvosok Lapja
How tail biting develops:
Tail biting is an aggressive behaviour that appears at the nursery 2-3 weeks after weaning. Main reasons include high stocking density, big groups and limited feeding space but contributing factors include genetics and dietary issues such as inappropriate protein content or amino acid profile and low fibre content. This behaviour acquired at the nursery continues during fattening, negatively affecting the productivity of the fattening phase as well. Rearing breeding gilts represents a huge risk factor for tail biting as it can be elicited by the hunger and aggression caused by restricted feeding. The animals in the group can have various “statuses” regarding the tail biting, there are pigs that are biters and also bitten, some that are only biters or only bitten, while some remain neutral and are unaffected by this aggression. Hunger and the resulting aggression act as catalysers in the process. Smaller pigs bite the tails of their penmates while they are eating to scare them away from the feeders and have access to feed. The bite wounds on the tail are then targeted by other animals, sometimes even out of curiosity. The wounded, bleeding tail then opens the door for pathogens and facilitates the development of various diseases. The bitten animal consequently has to be treated with antibiotics. In more severe cases the tail disappears totally, up to its base at the spine. If tail biting appears in a group of animals, both the aggressive and the wounded animals have to be placed in separate pens.
Prevention:
The animals in the group will become restless 2-3 days before the tail biting becomes apparent. They will spend less time resting, their tail is pulled in and seem to be searching around continuously. The identification of these signs relies on experience, time and attention (from the farmer or the manager) but is of utmost importance because this is the phase when we have a chance of preventing tail biting. First of all some animals have to be removed from the group to lower stocking density and allow better access to the feeders. Another option is to place additional feeders in the pen. To decrease stress caused by the unstimulating environment enrichment may be provided as a preventive measure. This should provide entertainment for the animals for sustained amounts of time, they should not lose interest in the provided items within a few days. The best solution is to provide natural materials such as long strands of straw (this is only recommended for full floors), tree stumps with the bark on or hemp ropes tied to the sides of the pen. Plastic or metal items (such as 20 l jugs, metal chains) will exert the desired effect for a short time only, the animals will lose interest and look for other ways to fulfil their behavioural needs.
Nutritional solutions:
The quality of the feed plays a key role in the development of tail biting. Feed should provide adequate amounts of crude protein, crude fibres and amino acids but also appropriate amounts of macro elements, trace elements as well as vitamins to fulfil the nutritional requirements of the given age group. Crude protein should be provided from readily digestible sources. Regarding macro elements, special attention should be paid to providing sodium in appropriate amounts as the optimum differs according to age groups. Sodium levels should be between 0.20% and 0.28% percent in the various finished feeds. Magnesium provided in an adequate form contributes to decreasing aggression by increasing water retention in the gut, thus providing an increased feeling of satiety. However, overdosing magnesium may lead to diarrhoea, so the fed amount should be determined precisely.
Stress induced behaviour in pigs such as tail biting may be triggered by a number of unfavourable environmental factors. These factors increase aggression and decrease well-being, also contributing to economic losses and health issues in large scale pig farming. Although nutrition is an important factor, it is not the exclusive reason for tail biting. Stress levels have to be lowered by providing environmental enrichment, reducing stocking density and providing adequate access to feeders. Adequate nutrition, appropriate nutritional composition and providing minerals may contribute to preventing behavioural problems, but addressing environmental and management factors are key to preventing tail biting.
Literature is available at request.
Bence Császár
junior swine consultant
Bonafarm-Bábolna Takarmány Ltd.
