Bovine perinatology: Current understanding and future developments

In human medicine, continuous intra-partum fetal monitoring is standard procedure;in cattle practice it is carried out rarely so that recognition of dystocia is often delayed.Hence, continuous severe traction and iatrogenic fetal trauma may occur leading tocompromised perinates. Approximately 75% of bovine perinatal mortality occurs withinthat critical one hour transition period after birth when those at-risk perinates fail to adaptto their extra-uterine environment. Despite improvements in general herd health andproductivity, perinatal calf mortality rates remain unacceptably high and are risinginternationally. In a recent review, calf mortality rates worldwide varied between 2 and10%, with losses of up to 15% in Holstein primiparae. These high loss rates are a realsocietal welfare concern and suggest that our current understanding of bovineperinatology is inadequate. For example, why does an increasing proportion of perinatalmortality occur following eutocia - idiopathic stillbirth or weak calf syndrome? The maincauses of bovine perinatal mortality are, in descending order of importance, combinedrespiratory and metabolic acidosis, parturient trauma, hypoglobulinemia, congenitalinfections, nutritional deficiencies, and omphalophlebitis. This review presents the latestfindings, from basic and applied research, on bovine perinatology and postulates itsfuture development given our current knowledge and recent advances. There is currentlya paucity of empirical data on near-term bovine fetal annexes and fetal well-beingassessments. However, the increased application of assisted reproduction technologies invaluable, high genetic merit cattle and the increased fetal mortality rates associated withthese pregnancies - including the abnormal offspring syndrome - has advanced ourunderstanding of bovine perinatology and pediatrics. These advances include ultrasonographic monitoring of fetal size and heart rate, use of biomarkers to detectplacental dysfunction, ultrasonic transit-time measurement of umbilical blood flow andimpulse oscillometry respiratory function monitoring. Likely future developmentsinclude the use of genomic selection, exploiting the recently mapped bovine genome, tobreed for reduced dystocia and stillbirth using sharper phenotypes. Also, development ofparturient ethograms combined with point-of-care sensor technologies to accuratelypredict onset of parturition and continuous fetal monitoring during parturition to detectreduced vitality by, for example, capillary blood gas analysis, pulse oximetry orcardiotography. Refinement of current therapeutic protocols may assist resuscitation ofcompromised perinates, improved periparturient pain management, and use of a morestandardised forensic necropsy work-up after stillbirth may all contribute. The emergenceand development of bovine perinatology as a specialised field of research represents anopportunity and a challenge for animal scientists globally to improve our currentunderstanding and lower bovine perinatal mortality rates.