Occasionally sows will attack their own piglets – usually soon after birth – causing injury or death. In extreme cases, where feasible, outright cannibalism will occur and the sow will eat the piglets. The development of this behaviour is often complex and difficult to stop and can cause significant losses.

Fig 1: The newborn piglet is especially vulnerable to attack.

Fig 2: Allowing gilts and sows to settle in crates well before farrowing may reduce savaging risks

Fig 3: Boxing piglets away during farrowing may reduce the risk of savaging.

Development and Presentation

Savaging of piglets most commonly occurs in gilt litters (but is not always restricted to them). This tends to mean that major problems are restricted to new herds where all farrowings are gilts. There are a number of particular factors that may trigger gilts to savage.

1. In the indoor farm in the UK, the immediate pre-farrowing period is likely to be the first time that gilts are confined in crates and as such they can be extremely agitated. The effect at farrowing time can be worse if the gilt has had little time to settle down e.g. farrows the day after crating. Similarly, gilts not given time to settle and nest build outdoors can be agitated and prone to aggression.
   
2. The general management of gilts after service and leading up to farrowing can also affect gilt behaviour. The more human contact gilts have during pregnancy, the less wary they will be when crated.
   
3. Agitation may also increase due to the sudden drop in food intake needed before farrowing to prevent milking and physical problems.
   
4. The stockman behaviour within the farrowing area will also influence gilt (and sow) behaviour. A noisy agitated stockman will tend to put pigs ‘on edge’ whereas one who quietly goes about his tasks will be more settling.
   
5. The discomfort of farrowing may act as a trigger for aggression in the gilt exacerbated by large pigs in small litters. The larger the litter and hence smaller the individuals, the less painful may farrowing be.
   
6. Cascade effect. In the same way that, within a room, one sow calling its litter to suck has the effect of triggering other sows to do likewise, an aggressive gilt or sow attacking a piglet can trigger others to the same behaviour.
   
7. Cross - fostering. If pigs are boxed away at birth and then distributed, less problems tend to occur, but if the gilt has suckled some of her own litter and litters are then swapped within the first 12 – 24 hours she may react against the fosterlings, causing damage.

Outcomes

Not uncommonly the whole or part of the litter may simply be found dead or parts of their bodies left in the pen. However, occasionally only single pigs may be attacked. The action to take will depend on the degree of damage done. If severe then euthanasia of the piglet is the only realistic and humane option. If however only skin damage occurs this can be sutured or stapled together and in general rapid healing will occur. Antibiotic cover, assisted suckling and avoidance of chilling should form part of the nursing care.

Impact

Clearly the economic impact of savaging is determined by the number of pigs that are lost as a result. Some farms can experience ongoing problems which can add 1% to mortality, equating to a loss of 120 piglets per year in a 500 sow herd. At an individual value of £35 per piglet (sale value minus feed cost) this equates to more than £4,000 per year.

In a severe start up herd problem, a 300 sow herd experienced savaging in 50% of gilt litters with the total number of piglets killed by gilts reaching 426 over 6 months equivalent to a loss of £15,000.