Parent-offspring conflict
in pigs
E.A. Pajor1,2, D. Fraser2
and D.L. Kramer1
1McGill University, Montreal,
Canada; 2Agriculture and Agri-Food Canada, Ottawa, Canada
Preliminary results of
an experiment to test parent-offspring conflict theory are presented.
Parent-offspring conflict theory predicts that sows and piglets should
be in conflict over the amount of parental investment (PI) in the litter
as the lactation advances. We tested this hypothesis and examined
potential tactics used by piglets to increase PI and potential counter-tactics
by the sow. 24 multiparous sows and litters were assigned to either
(1) a pen where the sow and litter were confined together throughout a
5 week lactation or (2) a "get-away" pen where the sow could leave
the litter at will.
In the confined treatment, sows lost significantly more weight during lactation
and took longer to
return to oestrus after
weaning. In the "get-away" treatment, piglets gained less weight
presumably because of lower milk production, but ate significantly more
creep feed. Piglets in get-away pens vocalized at the barrier to
the absent mother and had a higher rate of contact with the sow when she
was present. Sows in "get-away" pens gradually increased the amount
of time they spent away from their offspring and gradually decreased their
nursing frequency. Piglets of confined mothers spent more total time
in contact with the sow and sows lay on their udder more in an
apparent attempt to reduce
offspring stimulation. Thus piglets in confined pens and sows in
"get-away" pens can bias milk production in their favour. Maternal
control of milk output favours both farm animal welfare and production
efficiency.