In the last few years, our new research in sow nutrition has provided evidence that the traditional feeding regimen of gestating sows needs revision. In particular, the change of amino acid (AA) requirements from early to late gestation and the energy deficit of young sows in late gestation indicate that phase feeding of pregnant sows may be advantageous.   This article shows data obtained on the requirements of lysine, threonine, isoleucine and tryptophan in late and early gestating sows.  Also details on energy requirements during gestation are presented as well as the effect on the sows due to different feeding regimens.  It was found that switching to parity-segregated phase feeding of sows will save feed costs by supplying nutrients in the right amounts at the right time.