Projectleader Prof. dr. B.M. Spruijt
Centrum Welzijn Dieren,
Universiteit Utrecht
PhD-student Drs.
S. Dudink
Project period September 2001 – September 2005
Summary
There is ample
evidence that stressful conditions in
early life can have long-term consequences for behavioural and physiological
responsivity, and thus compromise welfare and health. Conversely, rewarding
events can have positive effects. Results of previous studies in rats indicate
that behaviour displayed in anticipation of reward reflects the history of the
animal, in particular with regards to the balance of stress and reward, and
thus is an indicator of the welfare status. In addition, endogenous opiods in
the brain have been implicated in reward anticipation, and may function as a
pivotal part of the neurobiological substrate of welfare status. In particular,
evidence indicates that release of endogenous opioids coincides with anticipation
of reward.
It is
hypothesised that, in pigs too, responses in anticipation of reward may be
useful indicators of the welfare status of the animal, and that frequent
exposure to reward may positively affect welfare and health. The aim of the project
is to test these hypotheses in piglets.
Conditions
routinely used in pig husbandry practice involve rearing of piglets in barren
pens and socially unstable groups (as a consequence of mixing), and early
weaning. Indeed, these conditions are stressful and known to exert long lasting
effects on the pigs behavioural and physiological responsivity and health that are adverse when compared with
rearing in enriched pens and socially stable groups. Piglets reared under these
contrasting conditions will be used to establish differences in anticipation of
reward (palatable food in a T-maze paradigm), validate these as differences in
welfare status using classical stress parameters, and assess the involvement of
endogenous opioids.
In addition,
the effects of intervention with frequent anticipation of food reward during
rearing on anticipatory responses in the T-maze and on the vulnerability
weaning diarrhoea under experimental conditions, the effects on villus/crypt
ratio and net absorption from the small intestine and on mesenteric flow rate
will be used as vulnerability parameters. The results of this project will (a)
contribute new insight into factors and mechanisms that determine welfare in
pigs, (b) yield a new, non-invasive, positive indicator for welfare, and (c)
open new strategies for the improvement of welfare and health of husbandry
animals.