Research Summary - 1
Relationship between Milk and Blood β-Hydroxybutyrate in Early Lactation Holstein Cows
| Date/Time: |
9/11/2025
16:45
|
| Author: |
Kathryn Bach |
| Clinic: |
Cornell University |
| City, State, ZIP: |
Ithaca, NY 14853 |
KD Bach, MS, VMD, PhD
1
;
CR Seely, MS, PhD
2
;
JAA McArt, DVM, PhD
1
;
1Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14850
2Department of Agriculture, Nutrition, and Food Systems, College of Life Sciences and Agriculture, University of New Hampshire, Durham, NH 03824
Introduction:
While blood β-hydroxybutyrate (BHB) measurement remains the gold standard for monitoring hyperketonemia (HYK) in early lactation dairy cattle, interest in milk BHB as a non-invasive proxy continues to grow. However, due to short-term variability and known diurnal fluctuations in blood BHB, as well as the unclear role of the mammary gland in BHB handling, the interpretation and application of milk BHB measurements remain incompletely understood. The objective of this study was to evaluate the relationship between milk and blood BHB concentrations in early lactation, and to assess how temporal aggregation of blood BHB measurements influence this relationship. We hypothesized that milk and blood BHB will be associated and that time-averaged blood BHB would strengthen this relationship by reducing short-term variability.
Materials and methods:
Twenty-eight multiparous Holstein cows between 3 and 9 DIM were enrolled during June and July of 2019 in a 5-day intensive sampling study. At enrollment, cows were fitted with a 14-gauge × 140-mm jugular catheter (Abbocath-T, Hospira, Sligo, Ireland) and 10 mL of blood were collected every 2 hours into EDTA vacutainer tubes (Becton Dickinson, Franklin Lakes, NJ) beginning 15:00 h on day 1 through 05:00 h on day 5. Plasma was harvested within 30 minutes of collection and stored at −80°C until blood BHB analysis at the New York State Animal Health Diagnostic Center (Ithaca, NY) using a commercially available kit (D-3 Hydroxybutyrate Ranbut, Randox Laboratories, Antrim, UK) on a Roche Cobas 6000 series, c501 Clinical Chemistry Automated Analyzer (Roche Diagnostics, Indianapolis, IN) according to manufacturer recommendations with daily calibration and controls. Milk production data and proportional composite milk samples were collected every 8 hours (06:00, 14:00, and 22:00 h) and milk samples analyzed at the Department of Food Science at Cornell University (Ithaca, NY) for milk BHB using mid-infrared Fourier Transform Infrared spectrometry (Delta Instruments, Model FTA, Drachten, NL). Data was analyzed, while accounting for repeated measures within cow, using PROC MIXED in SAS 9.4 (SAS Institute Inc., Cary, NC). Associations between milk BHB and blood BHB, while controlling for lactation group (LACT = 2, 3, and ≥4) and milk yield, were first evaluated using the three approaches: every 2-hour blood BHB, 8-hour time-averaged blood BHB (mean blood BHB concentrations in the 8-hour window prior to a milking event), and the most recent blood BHB sample prior to each milking event.
Results:
For all models, milk BHB was significantly associated with blood BHB (all p < 0.001). The estimated slopes for the every 2-hour model (slope = 7.03; SE = 0.36; t-value = 19.6) and 8-hour time-averaged model (slope = 7.01; SE = 0.60; t-value: 11.7) were similar, though the latter showed greater variability. The model using the most recent blood BHB value produced a slightly steeper slope (8.33; SE = 0.66; t = 12.8), but with no improvement in precision.
Significance:
These findings support a consistent association between milk and blood BHB concentrations across multiple modeling approaches. However, visual inspection of the data suggests that the strength of this relationship is limited, particularly at higher blood BHB concentrations. This highlights the need to delve deeper into the influence of milk yield, along with other factors like metabolic status, on this relationship.yield and metabolic status that may influence this relationship.
