Correlations between the different aspects of ketosis dynamics in dairy herds in the Benelux by using BHB-measurements in milk from the DeLaval Herd NavigatorTM.

BHB-concentrations is mostly used for detection hyperketonaemia. Most studies applied BHB-concentrations in blood and a few studies have used BHB-measurements in milk. On-set, duration and maximum BHB-concentrations are different aspects of ketosis dynamics. The aim of this study is to investigate how different parameters of ketosis dynamics correlate with each other and the second objective of this study is to investigate if the severity of keto-sis can be reflected in an area under the curve of the repeated BHB-measurements in milk detected with the DeLaval Herd NavigatorTM. Within the Herd Navigator an inline sampler inside the AMS automatically takes a representative sample of 80 ml milk from each indi-vidual cow during the milking process and measures BHB-concentrations at least daily from 3 to 20 days in milk and between 21 and 60 days in milk at least once every 4 days. The in-vestigated data, provided by Lattec, which included 48 herds working with the Herd Naviga-tor in the Benelux in June 2020. Data of unique calving’s between July 2018 and August 2019 were included. The final dataset included 130,247 BHB-measurements of 4030 unique calving’s. The cur-rent study defined three aspects of ketosis dynamics: the onset of ketosis, the duration of ke-tosis and the maximum BHB-concentration. Descriptive statistics were performed of the dif-ferent aspects of ketosis. Mean onset of ketosis was 18 DIM, 15 DIM and 12 DIM for cows with parity 1, 2 and 3+ respectively. Mean duration of ketosis was 21 days for cows with parity 1, 27 days parity 2 cows and 32 days for cows with parity 3+. The correlation between the onset of ketosis and the duration of ketosis was -0.546 (parity 2 cows), the correlation between the duration and maximum BHB-concentration was 0.460 (parity 2 cows). The area under the curve is calculated as a sum of all BHB-measurements between 3 and 60 DIM. The mean area under the curve was 3,67 for parity 1 cows, 4,14 for parity 2 cows and 4,63 for parity