Correlation between levels of β-hydroxybutyrate and fatty acids in blood and milk and its impact on ketosis diagnosis in dairy cows

SKC at herd level is difficult to diagnose. Poor production and reproduction performances are usually observed as an increased incidence of periparturient diseases in the herd (Suthar et al., 2013). Diagnosis methods include determination of beta-hydroxybutyrate (BHB) and increased non-esterified fatty acids (NEFA) resulting from body fat mobilization. BHB and NEFA could be dosed in blood of animals in late gestation and in early lactation. Post calving, cows presenting BHB over 1. 2-1.4 mmol/L are considered SCK-cows while those presenting NEFA over 0.6 mg/L are labelled fat mobilising cows. Development of non-invasive diagnosis techniques could be interesting to sample animals at a larger scale with lesser stress. The aim of this study was to verify whether blood and milk BHB values were correlated and whether diagnostic methods by milk analysis could be developed. Seventy -five cows out of 8 selected Walloon dairy herds were followed up monthly from calving to pregnancy diagnosis regarding production and reproduction. At each visit (V), BHB and NEFA levels were determined in milk and blood. A maximum of 5 V was made. BHB was determined in blood using a cow-side test and in milk by a colorimetric test . Blood NEFA and milk fatty acids were determined by gas chromatography (GC). Statistical analysis was performed by SAS 9.1. BHB levels in blood and milk were highly correlated (r= 0.86), indicating the possibility of diagnosis of SCK by milk sampling. The earliest the samples have been taken, the better the correlation is (r=0.95 V1; r = 0.91 V2). Comparison of BHB with NEFA demonstrated a better correlation with milk BHB than with blood BHB (respectively 0.51 and 0.53 in milk vs 0.41 and 0.48 in blood for the V1 and V2 respectively). After the 2d V, the correlation dropped to 0.38 (V3) and -0.14 (V4).To conclude, dosage of milk BHB could be a good indicator for ketosis diagnosis taking into account that correlation with blood BHB and with NEFA is time-related.