Milk biomarkers to detect ketosis and negative energy balance using MIR spectrometry

In order to manage negative energy balance and ketosis in dairy farms, rapid and cost-effective detection is needed. Among the milk biomarkers, citrate was recently identified as an early indicator of negative energy balance and acetone and BHB are of particular interest regarding ketosis. The objective of this study was to evaluate the ability of Mid-Infrared (MIR) spectrometry to predict these biomarkers as this technology can routinely provide rapid and cost-effective predictions. A total of 566 milk samples were collected in commercial and experimental farms in Luxembourg, France and Germany. Acetone, BHB, and citrate contents were determined by flow injection analysis. Milk MIR spectra were recorded and standardized for all samples. Acetone content ranged from 20 to 3,355 μmol/l with an average of 103 μmol/l; BHB content ranged from 21.3 to 1,595.6 μmol/l with an average of 215.4 μmol/l; and citrate content ranged from 4.5 to 15.5 mmol/l with an average of 8.9 mmol/l. Acetone and BHB contents were log-transformed to approach a normal distribution. Prediction equations were developed using PLS. The R2 of calibration was 0.73 for acetone, 0.75 for BHB and 0.90 for citrate with RMSE (root mean square error) of 87.7 μmol/l, 86.5 μmol/l and 0.75 mmol/l respectively. An external validation was performed and RMSE of validation was 45.2 μmol/l for acetone, 65.33 μmol/l for BHB and 0.80 mmol/l for citrates. Although the practical usefulness of the equations developed should be verified with field data, results from this study demonstrated the potential of MIR spectrometry to predict citrate content with good accuracy and to supply indicative contents of BHB and acetone in milk, providing consequently detection tools of ketosis and negative energy balance in dairy farms.