Effects of the season on physiological and endocrine traits and on HSP70 in Saanen goats under Mediterranean climate conditions

This study was conducted to determine the impact of heat stress on some physiological and endocrine traits in Saanen goats raised under Mediterranean climate conditions. The effects of thermal stress on heart rate (HR), respiration rate (RR) and rectal temperature (RT) on plasma total trii-odothyronine (T3), thyroxine (T4), Cortisol (C), and HSP70 concentrations were evaluated on twenty two Saanen goats of different ages in the second week of April 2013, July 2013, October 2013 and January 2014. Climatic data such as temperature (°C) and relative humidity (%) were recorded from Spring 2013 to Winter 2014. Live body and BCS values were also recorded during this period. The physiological parameters above were measured twice on each experiment day (morning and afternoon) in all seasons. Blood samples were collected in each afternoon of the experiment day to analyze T3, T4 C, and HSP70. All data were analyzed. According to the values of rectal temperature (RT), it was estimated that the goats were under extreme heat stress only in the summer season. The heart rate (HR) values in the winter season for morning and noon periods were found statistically significant (p < 0.05). The average respiratory rate (RR) in the spring season was found significantly lower. On the other hand, the RR for the noon period in the summer was higher than in the fall and winter seasons (p < 0.05). There was a significant difference (p < 0.05) between summer and fall seasons for C values. The highest value (96.62 ng/ml) was obtained in spring, whereas the lowest (60.58 ng/ml) in the fall. T3 levels in the fall and winter were found to be statistically significant (p < 0.05). They were the highest in the winter and spring, and the lowest in fall. T4 and T4/T3 levels in the winter were found to be statistically higher than in other seasons (p < 0.05). The lowest value for T4 was found in the fall and for T4/T3 in summer. Mean HSP70 value in spring was found to be statistically low (p < 0.05). The changes in THI values in different seasons, particularly between mornings and afternoons, indicated that thermal stress was evident, and that the animals became resistant to it eventually. The fluctuations of the C, T3, T4 and HSP70 values were indicators of the animals’ reaction to thermal stress. The THI values in spring, which were between 16 and 18 THI, may be considered within the ideal comfort zone for goats. It was observed that Saanen goats were able to adapt to seasonal weather changes in the environmental conditions of the region.