Correlation between cardiac rhythm parameters and cytokine profile levels in young cattle during early neonatal ontogenesis

Background. During the growth and development of young cattle, there is a significant association between functional changes in the body and housing conditions, influencing the regulation of immune responses and metabolic processes. In calves kept in natural conditions, the activity of natural immunity regulators prevails, contributing to the optimisation of growth and development processes. At the same time, in young animals exposed to stressful conditions associated with intensive housing methods, a decrease in the activity of these regulators is recorded, which can negatively affect their health and adaptability. Activation of neurohumoral mechanisms, including the influence of the hypothalamic-pituitary system, plays a key role in the regulation of metabolic processes and the immune response in young animals. In calves under stress, an increase in the level of proinflammatory cytokines is noted, which indicates a violation of the physiological balance in the cytokine network. Conversely, in calves kept in more favorable (natural) conditions, a more balanced ratio between pro- and anti-inflammatory cytokines is observed, contributing to the maintenance of homeostasis and improved adaptive responses.

Purpose. The main objective of the present research is to find out the correlation between cardiac rhythm parameters and cytokine profile levels in young cattle during early neonatal ontogenesis.

Materials and methods. To study the nature of the correlation between the parameters of the heart rate and the levels of cytokines in young cattle in early neonatal ontogenesis, 50 one-day-old calves aged 5 days were randomly selected at the premises of Chapaevskoye SP LLC.

In the first experimental group, after calving, the newborn calf underwent a primary veterinary examination, after which it was left in a group with its mother, simulating natural conditions for the entire duration of the experiment.

In the second experimental group, calves were managed according to industrial livestock farming practices. Newborn calves were separated from their mothers immediately after birth and fed with colostrum: two liters within 1-2 hours after birth, followed by an additional two liters by the 12th hour of life. This approach subjected the animals to higher adaptive and domestication stress. Statistical significance was determined in relation to the second experimental group.

The calves of all groups underwent heart rate analysis at 5 days of age; the animals were examined in a standing position, in a stall, and in a lateral lying position on an isolated surface using a diagnostic device, a single-channel electrocardiograph EK1T-07 “Axion”.

Blood samples were collected aseptically from the tail vein of each experimental group using S-Monovette 1.2 ml (66x8 mm) KZ-EDTA tubes. In stabilized samples, cytokine levels in blood plasma were measured using flow cytometry on a Bio-Plex Protein Assay System (Bio-Rad, USA). The Human 8-Plex Cytokine Panel reagent kit was used for the analysis according to the manufacturer’s instructions. As a result of the study, four types of cytokines were quantitatively measured: interleukin-2 (IL-2), interleukin-4 (IL-4), interleukin-8 (IL-8), and interleukin-10 (IL-10).

To ensure data reliability, cytokine concentrations were determined in three independent experimental series, both for calibration solutions and for the analyzed samples. Quantification was determined in pg/ml using Bio-Plex Manager 6.1 software (Bio-Rad) based on standard calibration curves. The obtained data were processed using descriptive and structural statistics.

To analyze the relationships between various heart rate parameters and cytokine levels in young cattle, the statistical method of Pearson correlation (r) was used, determining the degree and direction of the relationship between variables, which is critical for understanding physiological processes and their impact on animal health.

Results. Increased activity of the autonomic mechanisms regulating heart rate in newborn calves was associated with reduced function of innate immunity regulators (IL-8), specific immune responses (IL-2 and IL-4), and cytokines involved in inflammatory processes (IL-10). A weak relationship was also found between the activity of the autonomic nervous system, reflected in the very low frequency component (VLF) of heart rate variability, and the level of IL-4. The increased influence of the central nervous system on cardiac activity, including activation of the hypothalamic-pituitary axis, is accompanied by an increase in the concentration of IL-4, which plays an important role in the differentiation of lymphocytes and the development of the immune response, including inflammatory reactions.

Conclusion. Analysis of the heart rate dynamics confirmed that under stress conditions, an activation of the autonomous regulatory circuit is observed, which can negatively affect the health of calves. An increase in the activity of low-frequency waves is associated with increased sympathetic activity and stress, while high-frequency waves correlate with the activity of the parasympathetic nervous system and improved adaptive mechanisms.

Thus, the study highlights the critical importance of optimizing housing conditions for newborn calves. Correction of environmental factors and minimization of stress are essential to ensure harmonious interaction between central and autonomic regulation. This, in turn, can contribute to improved health, strengthening of the immune response and increased survival of newborn offspring, as well as the effectiveness of adaptation of young cattle in early neonatal ontogenesis.