Piglet savaging by gilts
and sows: Some possible causes
M. Harris and H. Gonyou
Prairie Swine Centre
Inc., Saskatoon, Canada
Piglet savaging occurs
when aggressive behaviour is displayed by a sow or gilt towards her newborn
offspring. In most cases, no injury occurs; however, piglets may
be severely injured or killed, and dead piglets are sometimes eaten or
partly eaten. Usually, the first piglet(s) only are affected, but
multiple savaging attempts may be made which result in the death of the
whole litter. Aggressive behaviour usually stops once one or two
piglets have successfully suckled. Savaging is more common in gilts
than sows, possibly due to immaturity or inexperience. However, since
most producers select against savaging gilts, the importance of the "gilt
factor" is hard to estimate. Estimates of incidence of
attacks vary widely,
from 0.2-0.3% (Backstrom, 1973) to 89% gilts and 20-25% sows (English,
Smith & MacLean, 1977). Differences in definitions of savaging,
as well as minor occurrences escaping attention, may be two reasons for
this disparity. Savaging behaviour has only been observed in intensive
agriculture situations. This may be due to inadequate opportunity
to observe farrowings in feral or free-ranging conditions; alternatively,
the behaviour may be induced in intensive animals by some aspect of management
or environment. Very little is known about the causes
of piglet-directed aggression
in sows. Genetic studies have shown the behaviour to be moderate
to highly heritable (0.4-0.9, Knap & Merks, 1987). Timing of
hormonal changes around parturition may facilitate aggression. Oxytocin
suppression, caused by stress, may delay or prolong farrowing, and may
also predispose to aggressive behaviour. Many environmental factors
may be implicated in savaging behaviour: for example, type of accommodation,
disturbance at farrowing, and physical factors such as temperature and
humidity. "Maternal" temperament in gilts is another possible
field of investigation.
Lack of suitable personality traits in some feral gilts might lead them
to fail to reproduce; managed gilts, however, will be mated regardless
of temperament.