L
ameness is
a frequently occurring, p
ain
ful condition o
f breeding sows th
at
may result in hyper
algesi
a, i.e.,
an incre
ased sensitivity to p
ain. In this study
a mech
anic
al nociception threshold (MT) test w
as used (1) to deter
mine i
f hyper
algesi
a occurs in sows with n
atur
ally-occurring l
ameness; (2) to co
mp
are
me
asure
ments obt
ained with
a h
and-held probe
and
a li
mb-
mounted
actu
ator connected to
a digit
al
algo
meter;
and (3) to investig
ate the syste
matic le
ft-to-right
and cr
ani
al-to-c
aud
al di
fferences in MT. Twenty-eight pregn
ant sows were investig
ated, o
f which 14 were
moder
ately l
ame
and 14 were not l
ame.
Over three testing sessions, repeated measurements were taken at 5 min intervals on the dorsal aspects of the metatarsi and metacarpi of all limbs. The MT was defined as the force in Newtons (N) that elicited an avoidance response, and this parameter was found to be lower in limbs affected by lameness than in normal limbs (m>Pm> < 0.05). Forelimbs had higher MTs than hindlimbs (m>Pm> < 0.001). The hand-held probe systematically yielded lower values than the actuator (m>Pm> < 0.001), and the MT differed between morning and afternoon testing sessions (m>Pm> < 0.001), as well as between days (m>Pm> < 0.001). The findings provide evidence that lame sows experience hyperalgesia. Systematic differences between forelimb and hindlimb MT must be taken into account when such assessments are performed.
