Abstract :
Genetic selection and better control of the environment of the pigs have resulted in increased production levels concerning
both reproduction and growth. Such high performances imply high physiological demands that may deteriorate health and
welfare. The aims of this paper are to review the physiological challenges that pigs are facing, to identify possible
consequences on health and welfare, to propose ways of detecting and correcting problems whenever possible. At weaning,
piglets are submitted to abrupt changes in food supply, housing and social environment. Behavioural changes and efficient
adaptations of the digestive tract are critical for their health and welfare. Physiological demands to support these adaptations
and risks of failure are inversely related to the age of the pigs. During fattening, modern pigs have high daily weight gain
especially of lean tissue as well as elevated feed conversion rate. These high growth performances are suspected to favour
stress and disease susceptibility, undesirable behaviours as well as leg weakness, but further experimental data are necessary
to validate these effects and find their origin. In reproductive females, high prolificacy generates elevated foetal demands for
nutrients and space that are not fully met as shown by an increased number of light piglets having difficulties to adapt
successfully to the neonatal life. During lactation, sows with high milk production have high nutrient requirements leading to
intense catabolism that may affect their health, welfare and future reproductive abilities.
