Lactate dehydrogenase (LDH) is widely used as a nonspecific marker of tissue damage and cellular turnover and has been associated with metabolic and inflammatory processes, but its relationship with automated monitoring data and blood biochemical indicators in early-lactation dairy cows is still not well described. The aim of this study was to evaluate associations between LDH activity, blood biochemical parameters, and automated monitoring indicators in early-lactation Holstein cows. A total of 91 clinically healthy cows were classified into two groups according to LDH activity: Group 1 (LDH < 1364 U/L; n = 53) and Group 2 (LDH ≥ 1364 U/L; n = 38). Blood samples were collected once per cow during early lactation, whereas automated monitoring parameters were continuously recorded and daily averages corresponding to the sampling day were used for analysis. Cows with higher LDH activity had significantly higher aspartate aminotransferase (AST) activity and moderate increases in albumin (ALB), creatinine (CREA), gamma-glutamyl transferase (GGT), calcium (Ca), phosphorus (PHOS), and iron (Fe). Correlation analysis showed a strong positive association between LDH and AST (r = 0.799, p < 0.001), while moderate positive correlations were observed with ALB, alanine aminotransferase (ALT), CREA, Ca, GGT, Fe, and PHOS. Receiver operating characteristic (ROC) analysis showed the best discrimination ability for AST, while CREA, ALB, Fe, PHOS, Ca, and GGT showed moderate classification performance. Automated monitoring parameters did not differ significantly between groups; however, cows with higher LDH activity tended to show lower rumination time together with higher milk electrical conductivity, higher milk yield, higher fat-to-protein ratio (FPR), and higher somatic cell count (SCC). Overall, the results indicate that LDH is more closely related to systemic biochemical variation than to immediate changes in production or behavioral indicators, and support the use of biochemical markers together with automated monitoring data when evaluating physiological adaptation during early lactation.

Rumination time is considered a sensitive behavioral indicator of physiological and metabolic status in dairy cows, yet its relationships with biochemical and milk quality parameters under commercial robotic milking conditions remain insufficiently described. This study combined precision monitoring technologies, serum biochemical profiling, and in-line milk analysis to evaluate physiological differences among early-lactation Holstein cows according to rumination time. A total of 88 cows were classified into three rumination time categories (>527, 412–527, and <412 min/day). Milk production traits, milk quality indicators, and blood biochemical parameters were compared among groups, and univariable regression analysis was performed to identify variables associated with rumination time. Cows in the low rumination group showed higher milk temperature, electrical conductivity, and somatic cell count, as well as lower milk protein percentage. They also showed higher concentrations of total protein, urea, gamma-glutamyl transferase, and lactate dehydrogenase, while triglyceride concentrations were lower. Regression analysis identified electrical milk conductivity, creatinine, magnesium, potassium, and chloride as variables associated with rumination time. These findings indicate that reduced rumination time is associated with changes in milk quality and biochemical parameters in early-lactation dairy cows, suggesting that rumination monitoring may provide useful information for identifying cows experiencing physiological and metabolic challenges under commercial farming conditions.

The transition period is a physiologically demanding stage in primiparous dairy cows, as the onset of lactation occurs simultaneously with continued growth. This longitudinal study initially enrolled 22 primiparous Holstein dairy cows. Eight cows that developed transition disorders during the monitoring period were excluded according to the predefined study protocol. Therefore, the final analysis included 14 clinically healthy primiparous Holstein dairy cows monitored from four weeks before calving to five weeks postpartum to characterize normal physiological adaptation during the transition period. Cows were monitored using continuous intraruminal sensors and automated milk analysis systems, while blood samples were collected weekly and analysed using linear mixed models with repeated measurements. Milk yield increased from 17.9 kg/day in week +1 to 26.3 kg/day in week +5 (a relative increase of 47%). Significant temporal changes were observed in iron (Fe), phosphorus (P), glucose (GLUC), triglycerides (TRIG), urea (UREA), albumin (ALB), and alanine aminotransferase (ALT). Serum Fe decreased from 30.9 µmol/L at week −2 to 14.5 µmol/L at week +2 (−53%), while P declined from 2.95 mmol/L at week +1 to 1.41 mmol/L at week +2 (−52%). Sensor data showed reduced physical activity (−59%) and increased water intake from 60.6 L/day in week −4 to 99.4 L/day in week +1, whereas rumination time and rumen pH remained relatively stable. Correlation analysis identified significant associations among milk yield, metabolic variables, and behavioural indicators. These findings suggest coordinated physiological adaptation during the transition period and support the use of combined blood and sensor-based monitoring to better understand early-lactation dynamics in primiparous dairy cows.

Balantioides coli is an enteric ciliated protozoan detected in cattle, but the association between microscopic B. coli counts and precision dairy-farming indicators remains poorly understood. This cross-sectional study evaluated associations between microscopic B. coli counts and behavioral, production and milk-composition traits in 83 clinically healthy Holstein cows in parity 2–4 and 20–100 days in milk. Fecal samples were examinated using sedimentation and modified McMaster methods and abundance was expressed as microscopic counts per field of view. Automated farm systems provided eating and rumination times, daily milk yield, milk fat-to-protein ratio, lactose concentration and somatic cell count. Zero-order correlations between microscopic B. coli counts and all evaluated indicators were weak and non-significant (r = 0.027–0.190). After adjustment for parity and days in milk, a modest positive correlation was observed with lactose concentration (partial r = 0.296, p = 0.007). The remaining adjusted correlations were weak or negligible and statistically non-significant: eating time (r = 0.105), rumination time (r = 0.036), daily milk yield (r = 0.060), milk fat-to-protein ratio (r = 0.064) and log10-transformed somatic cell count (r = 0.015). Overall, microscopic B. coli abundance showed limited association with the evaluated indicators, and the lactose finding should be regarded as exploratory.