Energy and protein requirements of sows can vary widely according to p
hysiological stage, reproductive performance, behaviour and housing co
nditions. It is why we propose to calculate these nutritional requirem
ents by the factorial approach, in order to determine a feeding strate
gy that allows to maintain adequate body reserves over the whole repro
ductive life, and minimize reproductive disorders. During lactation th
e energy requirements are high and closely related to milk production,
whereas in pregnancy they are low and mainly affected by the housing
conditions or the behaviour of the animal. In the same way, amino acid
s requirements are rather low in pregnancy and they increase drastical
ly in lactation, according to the high protein output in milk and the
insufficient appetite of the sow during that period. Thus, it is recom
mended to adapt the composition of the diet according to the nutrition
al requirement of each physiological stage.