Sow body weight, leanness and litter size have improved over the last 10 years, indicating increased amino acid and energy requirements. In addition, fetal weight and protein gain increase in late gestation so that requirements for amino acids and energy must change over the course of gestation. Models for amino acid and energy requirements of pregnant sows agree that requirements in late gestation are greater than in early gestation.  The purpose of this study was to find the requirements in early and late gestation using the indicator amino acid oxidation technique with concurrent indirect calorimetry in sows given constant feed allowance in their 2nd to 4th pregnancies.  It was found that Parity-segregated phase feeding of pregnant sows supplies the amino acids and energy necessary to match the sows’ requirements. This can result in reduced feed cost, better sow condition at farrowing, better rebreeding success and prolonged productive life of sows.