Biochemical indicators of adaptation and stress across seasons in Brown Swiss dairy cows

Investigation of the seasonal dynamics of blood biochemical indicators in dairy cows is a key prerequisite for effective herd management, prevention of metabolic disorders and improvement of animals’ adaptive resilience under various housing conditions. This article presents the results of a comprehensive study on the seasonal changes of blood biochemical parameters in Brown Swiss cows at 130–140 days of the second lactation under year-round tie-stall housing in the central region of Ukraine. It was found that the seasonal factor has a significant impact on several metabolic and adaptive biomarkers. In summer compared to spring, aspartate aminotransferase (AST) activity increased by 19.1 % (up to 103.9 ± 22.3 U/L; p = 0.0457), while in autumn the increase was 24.3 % (up to 108.5 ± 22.5 U/L; p = 0.0106). Alanine aminotransferase (ALT) in summer increased by 27.1 % (up to 47.4 ± 10.8 U/L; p = 0.0325). In autumn, the concentration of total calcium decreased by 16.2% compared to spring (2.07 ± 0.07 mmol/L versus 2.47 ± 0.08 mmol/l; p = 0.00001), and the Ca/P ratio fell by 25 % (1.11 ± 0.11 versus 1.48 ± 0.18; p = 0.00005). Autumn glucose levels increased by 52.9 % (up to 3.44 ± 0.14 mmol/L; p = 0.00003), while β-hydroxybutyrate decreased by 50.5 % in summer (to 0.32 ± 0.10 mmol/L; p = 0.0001). Total lipoproteins in autumn decreased by 19.3 % compared to spring (to 1054.8 ± 189.4 mg%; p = 0.0002). In summer, β-globulins were 37.8 % lower than in spring (15.8 ± 4.9 % versus 25.4 ± 8.9 %; p = 0.0051). High cortisol concentrations in summer and autumn (up to 37.2 ± 27.1 nmol/L; p = 0.0001–0.0008) confirm the activation of the stress axis under adverse conditions. The results of this study may be used for the implementation of metabolic status monitoring systems, the development of adaptive feeding and veterinary strategies, and for the improvement of heat stress prevention programmes, as well as increased productivity of cows during different seasons.