Prepartum serum hormone concentrations related to dystocia in Holstein heifers

Twelve Holstein heifers from a herd having a high incidence of dystocia were bled each day at 0730 h from 260 days gestation until parturition. The blood was analyzed for estradiol-17beta, estrone, 17-hydroxyprogesterone, progesterone, and corticosteroids. Six of the animals had dystocia. The concentrations of estradiol-17beta were lower and the concentration of progesterone higher in dystocial animals during the prepartum period from 23 to 12 days. The prepartum patterns of secretion of corticosteroid, estrone, and 17-hydroxyprogesterone did not change significantly in the two groups between days 23 and 12 prepartum. The prepartum difference in serum estradiol-17beta and progesterone concentration between normal and dystocial animals suggests that the timing of hormone changes in preparation for parturition is delayed and not as pronounced in dystocial animals.