Dystocia in the Standardbred Mare: A Retrospective Study from 2004 to 2020

SIMPLE SUMMARY: In the equine species, dystocia, any impediment to normal parturition, is not frequent, but when it occurs it can quickly evolve into a critical situation. The aim of this study was to retrospectively describe the incidence, causes, categories of dystocia severity, resolution procedures and postpartum complications in Standardbred mares hospitalized in a Veterinary Teaching Hospital and evaluate the effects of dystocia on the clinical and blood parameters of their foals. In normal pregnancy, the incidence of dystocia was 4.9%. Stage II appeared significantly longer in dystocic delivery, and the occurrences of postpartum complications in mares and onset of neonatal disease in foals were more frequent after dystocia. This study also investigated, for the first time, foaling difficulty, dividing all dystocic deliveries into mild, moderate and severe dystocia. Therefore, even a short but physiologically abnormal delivery can pose a risk to the life of the newborn and determine complications in the mare. ABSTRACT: Dystocia as a prolonged stage II parturition (>30 min) was associated with a higher risk of complications. The hypothesis of the study was that any type of dystocia could affect the foal’s health, even when the stage II was <30 min. Clinical reports on 222 Standardbred mares and their foals hospitalized at the Veterinary Teaching Hospital of the University of Bologna from 2004 to 2020 were reviewed. Mares were divided into the Eutocia Group (165, eutocic delivery) and the Dystocia Group (57, dystocic delivery). The incidence of dystocia was 4.9%. Stage II was longer in the Dystocia Group (median 20 min) than in the Eutocia Group (median 12 min). All occurrences of dystocia were retrospectively classified into three categories of severity: mild, moderate and severe dystocia. The occurrence of postpartum complications in mares and neonatal diseases and failure of passive transfer of immunity in foals was higher in the Dystocia Group. Foal venous lactatemia and serum creatine kinase were significantly higher in the Dystocia Group (median 3.9 mmol/L; 262 UI/L respectively) than in the Eutocia Group (median 3.1 mmol/L; 187 UI/L respectively). The APGAR score was lower in the Dystocia Group (median 8) than in the Eutocia Group (median 10) and significantly lower in severe dystocia (median 3). The duration of stage II should not be considered the only parameter of dystocia in mares: even a rapid resolution of dystocia could pose health risks to the foal and the mare.