Levels of luteinizing hormone (LH), prolactin, progesterone, cortisol, estrone and estradiol-17~ were determined during the postpartum anestrous period in samples collected from six second-calf, crossbred, suckled beef cows. Blood samples were collected at 6-h intervals beginning 2 wk before expected parturition and continuing until 10 d after first postpartum estrus. Samples were also collecte...