EFFECTS OF FENPROSTALENE AND ESTRADIOL-17-BETA BENZOATE ON PARTURITION AND RETAINED PLACENTA IN DAIRY-COWS AND HEIFERS

It was hypothesized that a high dose of estrogen in conjunction with a long-acting PGF(2 alpha) analog would synchronize parturition within a narrow time frame and reduce the incidence of retained placenta. On d 276 of gestation, 14 animals (9 cows and 5 heifers) per group receiv ed a placebo (group A), 1 mg of fenprostalene (group B), 50 mg of estr adiol-17 beta benzoate (group C), or both (group D). Treatment with es tradiol-17 beta benzoate increased serum concentrations of estradiol-1 7 beta from 228 pg/ml at treatment to 642 and 683 pg/ml at 24 h posttr eatment for groups C and D, respectively. Concentration of estradiol-1 7 beta in group A increased gradually to 526 pg/ml at 24 h prepartum. Progesterone concentrations were reduced by fenprostalene but not by e stradiol-17 beta benzoate. Estradiol-17 beta benzoate did not reduce i ncidence of retained placenta in animals treated with fenprostalene (g roup B vs. group D) but tended to reduce incidence in uninduced animal s (group A vs. group C). Thus, short-term elevation of estradiol-17 be ta to normal prepartum concentrations did not regress the corpus luteu m, induce parturition, or reduce incidence of retained placenta. Howev er, elevation of estradiol-17 beta for longer periods might enhance pl acental separation. Conversely, fenprostalene induced calving approxim ately 2 d after treatment. In this study, 90% of animals treated with fenprostalene calved within a 20-h period, but with a high incidence o f retained placenta.