Antanaitis, Ramūnas (Lithuanian University of Health Sciences) Baumgartner, Walter (University of Veterinary Medicine Vienna) Tolkačiovaitė, Kotryna (Lithuanian University of Health Sciences) Arlauskaitė, Samanta (Lithuanian University of Health Sciences) Girdauskaitė, Akvilė (Lithuanian University of Health Sciences) Džermeikaitė, Karina (Lithuanian University of Health Sciences) Krištolaitytė, Justina (Lithuanian University of Health Sciences) This study hypothesizes that higher in-line milk lactose concentrations are indicative of enhanced dairy cow behaviors-including increased rumination, feeding, and locomotion activities-reflecting superior overall health and well-being. It posits that fluctuations in milk lactose levels have a substantial impact on the physiological and behavioral responses of dairy cows, thereby affecting their milk yields and compositions. Each cow's milk lactose, fat, protein, and fat-to-protein ratio were continuously monitored using the BROLIS HerdLine in-line milk analyzer (Brolis Sensor Technology, Vilnius, Lithuania). The RumiWatch noseband sensor (RWS; ITIN + HOCH GmbH, Fütterungstechnik, Liestal, Switzerland) was employed to measure the biomarkers of the rumination, feeding, and locomotion behavior. The measurements were recorded over 5 days at the same time (during morning milking). A total of 502 cows were examined. During these 5 days, 2510 measurements were taken. Based on the lactose content in their milk, the cows were divided into two categories: the first group consisted of cows with milk lactose levels below 4.70%, while the second group included cows with milk lactose levels of 4.70% or higher. Our study showed that cows with higher milk lactose concentrations (≥4.70%) produced significantly more milk (16.14% increase) but had a lower milk protein concentration (5.05% decrease) compared to cows with lower lactose levels. These cows also exhibited changes in rumination and feeding behaviors, as recorded by the RWS: there was an increase in the mastication and rumination behaviors, evidenced by a 14.09% rise in other chews and a 13.84% increase in rumination chews, along with a 16.70% boost in bolus activity. However, there was a notable 16.18% reduction in their physical activity, as measured by the change in time spent walking. eng doi:10.3390/ani14060836 https://phaidra.vetmeduni.ac.at/o:2976 2024 CC BY 4.0 International http://creativecommons.org/licenses/by/4.0/ article The Relation between Milk Lactose Concentration and the Rumination, Feeding, and Locomotion Behavior of Early-Lactation Dairy Cows Body Condition Score; Production Traits; Pressure Sensor; Glucose; System; Yield; Associations; Validation; Indicators; Weight MDPI Animals 14(6) (2024) application/pdf