Fig. 1

Relationships between increase of P4 levels after ovulation, embryonic development, and IFNT production. There is a close association between poor embryonic development with low IFNT production and the subsequent low P4 levels in cows. Furthermore, P4 supplementation during the early luteal phase results in an improved embryonic development and increased IFNT production. These findings indicate that one of the key hormones in the establishment of pregnancy and the control of embryonic development is the CL secreted P4