Aberrant behaviour of pigs taking the form of cannibalism against pen mates producing tail, ear, flank and vulva damage is generally grouped together as vice.

Vice in the feeding herd has been the focus of much interest of late with Quality Assurance standards increasing their requirements for environmental enrichment. Whilst such provision is to be applauded, it is simplistic to consider boredom as the only, or even the principal, cause of the problem. Environmental insults resulting from draughts, temperature variation, overstocking, understocking, mixing, uneven batching combined with nutritional inadequacy and concurrent diseases are some of the more common factors triggering the problem. Tail docking in the first few days of life remains the most reliable method of prevention of tail biting but of course does little to prevent ear and flank damage.

The three-year picture of vice in growing pigs (graph1G) shows suggestions of a cyclical pattern with damage at its lowest in early summer and typically rising in the autumn – very noticeable in 2008 and 2009. Early reports for this year suggest a similar pattern will follow. Graph 2G indicates that where present, tail damage vastly exceeds that of ear and flank biting. (It is important to mention here that the commonly seen ear tip necrosis is NOT primarily a vice problem but relates more to skin infection, which can latterly progress to ear biting.)

It is also concerning to see that vice levels not only increase with increasing herd size but are also higher in finishing only farms, particularly compared to breeder/feeder farms (graphs 3G and 4G).

It is not surprising that more vice is reported in pigs kept on slats compared to straw (5G) but the data still explodes the myth that vice in growing pigs does not occur on straw.

Continuous flow systems report double the prevalence of vice compared to batches whilst indoor derived pigs are far more vulnerable than those reared outdoors. This may be consistent with the tendency for outdoor produced pigs to be straw bedded.

Within the sow herd, vulva-biting accounts for virtually all vice damage and is seen fairly consistently across all types of breeding herds (graph 1S). It should be noted that vulva-biting, which overall affects more than 1.0 per cent of all sows in the surveyed population, has only become a major issue since the ban on stalls and tethers for dry sows more than ten years ago. (Reports of vulva biting only relate to active cases – longstanding healed and scarred vulvas are not counted.)

The overall level of vulva biting has declined in 2010 following a fall off in the second half of 2009, prior to which it had been relatively consistent with no apparent seasonal pattern (graph 2S).

Regional differences in prevalence may reflect the differences in farm management but can also be distorted by a single farm outbreak in a short surveillance period - three months (e.g. graph 3S).

Within different management systems, however, some interesting patterns emerge (graph 4S).

Prevalence is much lower in straw systems than on slats – suggesting gut fill may play a part in the condition. The damage is also much greater in continuous flow farms compared to batch systems, which may suggest group stability plays a part. Of particular note is also the fact that whilst prevalence of vulva biting is much higher in indoor sows, 0.4 per cent of outdoor sows are also vulva bitten – a fact that is often overlooked or denied in the outdoor system.

Pigs are naturally aggressive to others and mutual damage is to some extent an inevitable consequence of farming; that is not to say that the pig industry and its advisors should accept these problems and must continue to strive to identify and rectify trigger factors and not be sidetracked by vested interests taking simplistic approaches to highly complex problems.