Subclinical hypocalcaemia follows specific time-related and severity patterns in post-partum Holstein cows

Hypocalcaemia is a common metabolic disorder of post-parturient dairy cows; enhancement our knowledge regarding Ca dynamics would improve cow health and welfare. This study investigated the presence time- severity-related subclinical hypocalcaemia (SCHCa) patterns in Holstein cows after calving their association with diseases during first week lactation. A total 938 from nine herds were blood sampled on days 1, 2, 4 8 post-partum, serum concentration was measured atomic absorption. Subclinical ketosis (serum β-hydroxybutyrate≥1.2 mmol/L) cases retained foetal membranes, metritis (MET), mastitis, displaced abomasum (DA) recorded. Using receiver operating characteristic (ROC) analysis, SCHCa cut-off identified at ≤ 2.09 mmol/L. Hierarchical two-step cluster analysis classified to seven clusters based test day records overall status. Two (NORM HIGH) included 318 normocalcaemic five (SCH-1 −5) those that least once subclinically hypocalcaemic (n = 620). second ROC performed order distinguish mild severe these 620 this 1.93 The associated risk disease clustership assessed generalized linear mixed models. Overall incidence 66.1%. Clusters SCH-1 SCH-2 short-term 1 respectively, while SCH-3 prolonged extending beyond. SCH-4 SCH-5 delayed SCHCa, which culminated 8, respectively. Compared NORM HIGH had lower MET no DA. Cows higher being diagnosed DA or any period. ketosis, disease. In conclusion, there are multiple differently risk.