Endocrine aspects of bovine dystocia with special reference to estrogens

Abstract

Little information is available concerning the role of hormones in dystocia. Data regarding the variability in estrogen production by the feto-placental unit are reviewed. Evidence is presented that the sire, or the breed of sire influences the amount of estrogens produced by the feto-placental unit, estimated as estrogen/creatinine ratio in the maternal urine during late pregnancy. The greatest differences were found in Zebu cows bred to Friesian bulls as compared to pure bred Zebus. Urinary estrogen excretion in late gestation was shown to be relatively low in Dutch Friesian cows bred to Charolais bulls and in MRI (Maas Rhine JIsel; Red and white) cows bred to bulls, known to cause a high incidence of dystocia in their offspring. These findings suggested a possible association of low urinary estrogen excretion, from day 260 of gestation to parturition, with a high incidence of dystocia. In a study of over 500 cows during late gestation over a period of 26 months, a seasonal influence on urinary estrogen excretion proved to be significant. The influence of season on dystocia is discussed. Because of a heritability of about .30 and a large variability between cows in urinary estrogen excretion, sire selection for urinary estrogen excretion is suggested as a tool in decreasing the incidence of dystocia.