Postmortem analysis of the causes of perinatal calf mortality on dairy farms

Bovine perinatal mortality (BPM) is a significant concern in dairy production owing to its economic and welfare implications. The objective of this study was to identify and classify the causes of perinatal calf mortality in Polish dairy farms using a clinicopathological investigative model. A total of 121 full-term calves (≥260 days gestation) that died before, during, or within 6 h of birth were collected from 29 farms. Each case underwent a detailed anamnesis, dam examination, and standardized necropsy. Based on the clinical, pathological, and anamnestic data, each case was assigned to one of the eight cause-of-death (COD) categories. Multinomial logistic regression and ANOVA were used to evaluate the associations between factors such as birth weight, calving difficulty, pregnancy length, foetal sex, and maternal parity and COD. Dystocia-related COD accounted for 47.1 % of all cases, with traumatic calving (traumotocia) being the most common subcategory. Other diagnosed causes included multifactorial origins (6.6 %), foetal malformations and intrauterine growth retardation (5.8 %), eutoxia (5.0 %), premature placental separation (1.7 %), anaemia (1.7 %), and infection (0.8 %). In 31.4 % of cases, no definitive cause could be determined. Dystocia was associated with significantly higher calf birth weight and longer gestation. Male calves had lower odds of dystocia than unexplained cases. Dystocia, particularly traumotocia, was the leading cause of BPM in dairy herds. This standardized clinicopathological investigative model can significantly improve diagnostic rates, although a notable proportion of cases remains unexplained. Enhancing perinatal outcomes will require improved calving management, judicious use of calving aids, and broader diagnostic support including laboratory testing.