The impact of physical and psychoemotional load on the physiological and hormonal status of German shepherds

In this article, we present the data on age-related changes in the concentration of protein and steroid hormones in German Shepherds depending on their physical and psychoemotional loads. We found that young animals (aged between one and three years) had increased body temperature, respiration rate, and pulse rate during training. After a five-minute rest, 1-year-old dogs demonstrated increased pulse rate of 135,56 ± 2.50 BPM (which is 20.17 % above the norm), respiration rate of 175.46 ± 2.51 breaths per minute (which is 80.85% above the norm), and body temperature of 40.02 ± 0.52 °C (which is 5% higher than that at rest). These parameters reach the baseline along with increasing of the rest time. A sixty-minute rest after training is insufficient to restore the physiological parameters in 1-year-old and 3-year-old dogs. In the case of adult dogs (aged 5-8 years), a sixty-minute rest after training ensures complete restoration of the general physiological parameters. The process of recovery is characterized by quantitative changes in the level of hormones, including thyroxine, triiodothyronine, cortisol, and thyrotropin-releasing hormone. These changes depend on the physical and psychoemotional load, as well as the age of the dogs. We found that the level of thyrotropin-releasing hormone increases with age and comprises 1.153 ± 0.086 mIU/L in the 1-year-old dogs and 1.471 ± 0.131 mIU/L in the 8-year-old dogs, whereas the physical and psychoemotional load do not have a significant impact on the level of thyrotropin-releasing hormone. The level of thyroxin increases with dogs’ age. Within our study, its concentration at rest was 27.32 ± 1.23 nmol/l in the 1-year-old dogs and 18.15 ± 0.45 nmol/l in the 8-year-old dogs. The level of thyroxin elevates during the training, which appears to be associated with a large expenditure of energy. The concentration of thyroxin reached 34.70 ± 1.34 nmol/l in the 1-year-old dogs after a five-minute rest, while the 8-year-old dogs had significantly lower levels of thyroxin that comprised 22.32 ± 0.38 nmol/l. A 24-hour rest after physical and psychoemotional load is sufficient to reduce the concentration of thyroxine to its baseline. The highest concentration of cortisol was observed in the 1-year-old and 3-year-old dogs, while the lowest concentration was found in the 8-year-old dogs. The level of cortisol decreased with age and was 278.30 ± 15.30 nmol/l and 184.60 ± 8.75 nmol/l among the 1-year-old dogs and 8-year-old dogs respectively. The concentration of cortisol substantially increases during training: up to 333.91±19.50 nmol/l in the 1-year-old dogs and 217.83 ± 6.20 nmol/l in the 8-year-old dogs. A 24-hour rest after training is insufficient for restoration of cortisol levels in the 1-year-old dogs, while in the 8-year-old dogs it comes back to the baseline within 24 hours. In conclusion, we should stress that the overall physiological parameters of service dogs and their hormonal status changes with age and depends on the physical and psychoemotional load. A 24-hour rest is insufficient for full restoration of physical condition of young dogs, while for adult dogs this period of rest is sufficient for restoration of their physiological condition, the dogs, therefore, may perform their duties.