Changes in haematological and serum biochemical parameter concentrations from the day of calving to ketosis onset in Holstein dairy cows during the postpartum period

Abstract Background Dairy cows commonly experience a negative energy balance (NEB) during early lactation as energy demands for maintenance and milk production exceed intake. Although most cows metabolically adapt to NEB and avoid ketosis, those that fail to adapt develop ketosis, which disrupts metabolism and reduces productivity. Haematological and serum biochemical parameters are crucial for understanding these metabolic disruptions. However, limited research has examined how these parameters change from calving to ketosis onset. This study aimed to investigate these changes, identify parameters associated with ketosis classification, and evaluate their implications for dairy cow health. Blood samples were collected from the jugular vein of Holstein cows and β-hydroxybutyrate (BHBA) was tested once every three days during the postpartum period (8 times in 21 days). Results Cows were categorised into three groups based on their highest BHBA concentration: non-ketosis (NK; BHBA < 1.2 mmol/L; n = 75), subclinical ketosis (SCK; BHBA ≥ 1.2 mmol/L and < 3.0 mmol/L; n = 46), and clinical ketosis (CK; BHBA ≥ 3.0 mmol/L; n = 35). The NK group had the highest red blood cell and monocyte counts, red cell distribution width, and alanine transaminase (ALT) concentrations. However, this group had the lowest mean corpuscular volume, mean corpuscular haemoglobin, non-esterified fatty acid (NEFA), and total bilirubin concentrations on the day of calving and at ketosis onset, followed by the SCK and CK groups (p < 0.05). In the NK group, counts of neutrophils, monocytes, and eosinophils, along with NEFA and lactate dehydrogenase (LDH) concentrations, decreased from the day of calving to ketosis onset. Conversely, ALT, aspartate transaminase (AST), and magnesium concentrations increased in the SCK and CK groups (p < 0.05). The NK group had the most pronounced changes in glucose, triglyceride, and magnesium and the lowest BHBA, LDH, and AST concentrations, followed by the SCK and CK groups (p < 0.05). Conclusions This study identified key haematological and serum biochemical changes associated with ketosis classification in dairy cows, highlighting metabolic adaptations in the NK group that mitigate ketosis risk and metabolic dysfunctions in the SCK and CK groups that develop ketosis. These findings provide practical markers for early detection and management of ketosis, supporting improved dairy cow health and productivity.