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This study hypothesizes that heat stress adversely affects dairy cows, resulting in reduced rumination, altering eating and drinking behaviors, changes in their locomotory patterns, and significant variations in their acid–base balance. The aim of this study was to investigate the impacts of heat stress on rumination, drinking, and locomotory behavior, as registered by innovative technologies, and acid–base balance in fresh multiparous dairy cows. This study was conducted during the summer, from 15 June to 8 July 2023, on a Lithuanian commercial dairy farm. We assessed 350 German Holstein cows that produced an average of 11,400 kg of milk annually throughout their second and subsequent lactation periods. We used the temperature–humidity index (THI) to divide the cows under investigation into three periods: I. high HS—THI >78 (period: 15–23 June 2023); II. medium HS—THI 72–78 (period: 24–30 June 2023); and III. low HS—THI p < 0.01); high mean differences were detected for rumination, which was 17.67% higher in the high HS period and 13.80% higher in the medium HS period compared to the low HS period (p < 0.01); and the change in activity was 12.82% higher in the low HS compared to the medium HS period (p < 0.01). Cows under high HS had higher blood urea nitrogen (BUN) levels compared with cows under medium HS (p < 0.01). The observed alterations in the rumination, drinking, and locomotory behaviors, in addition to the acid–base balance, highlight the multifaceted impacts of varying heat stress on the physiological and behavioral responses of dairy cows. This suggests that the utilization of advanced technologies may assist dairy farmers in effectively monitoring and controlling heat stress in cows. Additionally, regularly assessing blood urea nitrogen levels can enable farmers to modify their feeding practices, thus promoting optimal cow well-being and productivity.

The aim of our study was to investigate and quantify the impact of heat stress on the milk fat-to-protein ratio (F/P) and the metabolic profile in dairy cows, utilizing in-line registration methods for accurate and real-time data collection. This study was carried out in Lithuania at coordinates 55.819156, 23.773541, from 1 June 2023 until 31 August 2023. Milk composition, including fat and protein, was measured using a BROLIS HerdLine in-line milk analyzer from Brolis Sensor Technology, Vilnius, Lithuania. During the general clinical examinations (twice per week), blood samples were collected and determined for GLU—blood glucose concentration; BHB—blood β-hydroxybutyrate concentration; AST—aspartate transaminase activity; GGT—gamma-glutamyltransferase activity; and NEFAs—non-esterified fatty acids. The parameters based on the Temperature–Humidity Index (THI) were categorized into two groups: group 1, consisting of THI values less than 72, representing the comfort zone, and group 2, with THI values of 72 or higher, indicating a greater risk of thermal stress. Specifically, group 2 exhibited an 8.6% increase in the F/P ratio compared to group 1 (p = 0.049). Additionally, there was a 4.2% decrease in glucose levels in group 2 (p = 0.056) and a notable 5.8% decrease in albumin levels compared to group 1 (p < 0.001). We found a very weak, non-significant correlation between humidity and the milk fat-to-protein ratio (r = 0.043, p = 0.447) and a similarly negligible correlation with Beta-Hydroxybutyrate (BHB; r = 0.046, p = 0.417). We observed significant changes in milk composition, particularly an increase in the milk fat-to-protein ratio, and alterations in metabolic indicators like glucose, albumin, and liver enzymes. These changes, indicative of a negative energy balance and altered metabolic processes such as gluconeogenesis and lipolysis, correspond to previous research. The adoption of advanced tools, such as the BROLIS HerdLine analyzer, is recommended for the real-time monitoring of milk composition, which assists in the early detection of negative energy balances and metabolic issues. It is also crucial to adjust feeding practices to maintain energy balance during periods of high THI and to conduct regular health checks with a special focus on cows in early lactation.

This study delves into the effects of subclinical ketosis (SCK) and subclinical acidosis (SCA) on various parameters related to dairy cow rumination, eating, drinking and locomotion behavior. The research hypothesized that these subclinical metabolic disorders could affect behaviors such as rumination, feeding, and locomotion. A total of 320 dairy cows, with a focus on those in their second or subsequent lactation, producing an average of 12,000 kg/year milk in their previous lactation, were examined. These cows were classified into three groups: those with SCK, those with SCA, and healthy cows. The health status of the cows was determined based on the milk fat–protein ratio, blood beta-hydroxybutyrate, and the results of clinical examinations performed by a veterinarian. The data collected during the study included parameters from the RumiWatch sensors. The results revealed significant differences between the cows affected by SCK and the healthy cows, with reductions observed in the rumination time (17.47%) and various eating and chewing behaviors. These changes indicated that SCK had a substantial impact on the cows’ behavior. In the context of SCA, the study found significant reductions in Eating Time 2 (ET2) of 36.84% when compared to the healthy cows. Additionally, Eating Chews 2 (EC2) exhibited a significant reduction in the SCA group, with an average of 312.06 units (±17.93), compared to the healthy group’s average of 504.20 units (±18.87). These findings emphasize that SCA influences feeding behaviors and chewing activity, which can have implications for nutrient intake and overall cow health. The study also highlights the considerable impact of SCK on locomotion parameters, as the cows with SCK exhibited a 27.36% reduction in the walking time levels. These cows also displayed reductions in the Walking Time (WT), Other Activity Time (OAT), and Activity Change (AC). In conclusion, this research underscores the critical need for advanced strategies to prevent and manage subclinical metabolic disorders within the dairy farming industry. The study findings have far-reaching implications for enhancing the well-being and performance of dairy cattle. Effective management practices and detection methods are essential to mitigate the impact of SCK and SCA on dairy cow health and productivity, ultimately benefiting the dairy farming sector.