Influence of maternal and service-sire breed on serum progesterone and estrogen before calving and plasma 13,14-dihydro-15-keto-prostaglandin F2 alpha after calving.

Effects of breed of service sire and cow on birth weight and prepartum and postpartum endocrine function were studied in multiparous Brahman (n=20) and Angus (n=20) cows bred to Brahman or Angus bulls. Before calving, blood samples were collected on d 34 to 28, 27 to 21, 20 to 14, and 13 to 7, and after calving, samples were collected from d 0 to 7. Progesterone (P 4 ), estrogen (E 2 ), and 13,14-dihydro-15-keto-prostaglandin F 2α (PGFM) were quantified with RIA. Calves born to Brahman were smaller (P<.05) than calves born to Angus cows. Prepartum concentrations of