Altered Endocrine Profiles Contributing to Late Embryonic Mortality in Cattle

Abstract

Reproductive inefficiency is a critical barrier maximizing profitability and sustainability of cattle industries. While intensive management strategies have provided crucial information regarding the amount of pregnancy loss that occur in dairy cattle, beef cattle are less understood. Over 30 years of beef cattle research from around the globe was compiled to quantify pregnancy loss throughout different developmental stages of gestation. A clear gap in knowledge exists around the physiological mechanisms and endocrine profile contributing to pregnancy loss during late embryonic development when active placentation occurs. To study uterine-secreted products, a protocol was developed using a coccygeal vein catheter to sample blood at the site of uterine ovarian drainage in the vena cava of pregnant cows without negative consequences to the pregnancy. Cows with an increased likelihood of experiencing pregnancy loss have similar responses to oxytocin challenge as cows likely to maintain pregnancy at day 30 of gestation. Basal prostaglandin concentrations increased between day 30 and 40 of gestation without negative consequences to the pregnancy; however, late embryonic loss was affected by the pulsatility of prostaglandin F2α and prostaglandin E2 concentrations during this period. This foundational knowledge about the endocrine environment during active placentation lays the groundwork for future studies to understand the mechanisms of pregnancy loss and increase reproductive efficiency in both beef and dairy cattle herds.