NADIS monitors disease on pig farms on a day to day basis via a network of 14 specialist pig veterinary surgeons - has data to suggest that across the monitored population of close to 400,000 growing pigs, in the last three months the prevalence of tail biting is 1.2 per cent and that the prevalence in different systems highlights the widespread nature of the problem.

No one system of pig keeping is immune from tail biting. Slatted systems have seen a prevalence of 2% of pigs affected whilst on straw the figure is only 0.4 per cent. Indoor derived growing pigs are 50 per cent more likely to be tail bitten than those born outdoors. Damage to pigs tails by pen mates contributes a major loss to the pig industry.

Tail biting tends to be seen in a number of different scenarios ranging from a constant low grade problem in a continual production unit to explosive outbreaks in batches. As such, the incidence is highly variable.

In the former scenario, 3-5 per cent of pigs may be affected week in week out and it would be common place for 1 per cent to require euthanasia and a similar proportion to be condemned at slaughter (usually referred to as “pyaemia” on a condemnation sheet).

At this level, the cost to a 300 sow breeder feeder farm can be £10,000 per year (140 pigs per year lost) plus the costs of treatment, care, isolation and lost growth.

In a batch systems, losses as high as 30 per cent of pigs have been experienced – out of a batch of 700 pigs, 208 either died, were destroyed or were condemned at slaughter!

Natural behaviour or vice?

Pigs have a natural tendency to chew. They are also attracted to blood and once biting has started it tends to be infectious. In addition, pigs undergo teeth changes between 3-4 weeks of age and 7-8 months.

Anyone who has reared children will recognise the desire to chew during teething and this may be a component of piglet behaviour. Normal inquisitive investigation with the mouth can lead to “accidental” bleeding, which can lead to more serious damage.

In any given situation where tail biting occurs, there is a need to undertake a full investigation and assessment to identify the possible trigger factors. In many cases, a single rogue animal can be identified that has started the problem in a group – usually the smallest pig – although if not spotted early this animal may get lost in the group that join in.

A huge range of environmental, dietary and husbandry factors have been identified as acting as triggers for tail biting, ranging from stocking rates, temperature variation, competition for food and water, to Vitamin E deficiency and high fat diets.

Professional veterinary advice is essential to unravel the significant factors and identify the cause of “unhappy pigs”. Unfortunately, the “perfect” system has not been identified and, even if it could be, there are always likely to be cost constraints that will compromise its adoption!

It, therefore, unfortunately must be accepted that tail biting is a consequence of farming pigs and producers should attend to the basic biological needs of the pig to minimise the risk of damage.

Such areas for consideration include:-

1. Thermal comfort :- draughts, temperature variation, chilling and over-heating are highly significant factors.
2. Freely available feed and water – the pig that is unable to get to a free supply of feed and water is always more likely to seek revenge on its penmates.
3. Feed diets that are appropriate to the pig and contain a full balance of nutrients.
4. Stocking density. Space provision should be determined by the nature of the accommodation and the requirements of the specific pigs. The Welfare of Farmed Animals Regulations (2003) (the successor to The Welfare of Livestock Regulations 2000 & 1994) have done a great disservice to the pig.

Fig 1: Severely tail bitten pig requiring euthanasia	Fig 2: Alcathene piping can be a useful toy for pigs on slats

These regulations state the minimum space requirements for pigs of different weight. Putting aside the nonsense of a stepped graph (pigs of 19 and 20kg require the same space but those of 21kg require 50% more!) these minimum requirements have been interpreted as the optimum requirements. (A similar view is taken throughout Europe).

Producers must be aware that these figures were not based on any sustainable science and, as such, are totally meaningless to the true needs of the pig.

Concommittant disease is a major trigger of outbreaks of tail biting. The complex pathological and physiological factors brought into play by major systemic disease such as pneumonia, scour and wasting cause malcontent and aggression to develop, and tail biting is a common consequence.

November 2007