But we are told that grounds exist for believing some causal factors have more influence than others on the chances of an outbreak occurring. Specific examples mentioned are the absence of bedding (straw) and the presence of slatted floors. With straw, the advice given here is that full bedding is better than having only a limited amount available from a rack and long strands of the material are better than chopped pieces.

Scientists and some regulators have taken the view previously that pigs should have some object or material they can manipulate in aid of their welfare. Referring to toys or playthings probably gives the wrong idea, but the panel concludes there is little evidence that providing chains, chewing sticks or balls can reduce the risk of tail-biting.

Effects of feeding

We might have more success by starting with the pigs’ feed. Panel members say competition for feed and/or an inadequate feed intake tail-biting can lead to bitten tails. So too can feeding a diet that is inadequate for sodium or deficient in essential amino acids. Making a sudden change in diet composition is also criticised in this context, especially where the switch is to a mixture with a lower nutrient density.

Looking at these in slightly more detail, high feeding competition is said to be a tail-biting trigger if more than 10% of the pigs in the pen are waiting at any time to have access to the feed supply. Behavioural problems also can arise when re-filling of feeders is interrupted for over 12 hours in the case of pigs normally fed ad lib or for less than 12 hours in a rationed feeding regime of regular meals. The effect on behaviour from subjecting the pig to an abrupt change in feed could appear at any stage over the next 2 weeks. Similar consequences have been seen where pigs were exposed to multiple switchovers of feed type. Ingredient issues include an indication of tail-biting hazard if less than 0.17% sodium is present in the diet.

Management must play a role, of course. The EFSA committee warns about an increased risk of tail-biting if piglets are mixed again in the nursery after the usual mixing done at weaning time. Later on, the risk is that of having too high a stocking density in the pen, such as when exceeding 110kg of pig liveweight per square metre of floor area towards the end of the finishing period.

In relation to climate, the report comments that the risk of tail-biting seems to be increased in the autumn (fall) season of the year although others might say the opposite and claim it is summertime when the worst outbreaks are seen. The panel’s warnings elsewhere run from allowing the room temperature to be too hot — at least 3 degrees Celsius above the pig’s upper critical temperature limit — to too cold (at least 3 degrees below the lower critical temperature). Cold stress due to draughts comes into consideration when animals are exposed to a high air speed, it says, defined as above 0.5 metres per second. Poor air quality at times of low ventilation may mean an exposure to ammonia above 25ppm.

A checklist of such factors is recommended for use if tail-biting problems appear. Immediate actions put forward are to remove both the bitten pig and the biter from the pen. Moving the wounded animal to a newly-disinfected pen may help prevent infection of the tail wound. Tincture of iodine and wound sprays containing antibiotics can be applied to the tail to limit infections.