Daytime Evaluation of Oxidative Stress and Behavioural Parameters of Donkeys (Equus asinus) During The Hot-Dry and Cold-Dry (Harmattan) Season in a Tropical Savannah

The aim of the study was to evaluate oxidative stress and behavioural responses of donkeys during the cold-dry and hot-dry seasons. Thirty donkeys divided into three groups of ten donkeys each according to their age served as experimental subjects. During each season, behavioural and blood parameters of the donkeys were evaluated three times with an interval of one week at 06:00 h, 12:00 h and 18:00 h (GMT+1). During the hot-dry season, the peak dry-bulb temperature (DBT) value of 36.00 +/- 1.00 degrees C was recorded at 12:00 h, indicating that the season induced heat stress. The time spent feeding demonstrated diurnal fluctuations in adult, yearling and foal donkeys, with the highest time occurring at 12:00 h in both seasons. The malondialdehyde (MDA) concentrations in adults (2.34 +/- 0.14 nMol/L), yearlings (2.28 +/- 0.19 nMol/L) and foals (3.48 +/- 0.17 nMol/L) during the hot-dry season were significantly (P < 0.05) higher, when compared to the corresponding values (0.96 +/- 0.09, 1.18 +/- 0.10 and 1.82 +/- 0.10 nMol/L, respectively) recorded during the cold-dry season. At 0.3% NaCl-concentration, the percentage haemolysis obtained during the hot-dry season in adult (90.33 +/- 0.49%), yearling (91.24 +/- 0.88%) and foal (97.44 +/- 0.24%) donkeys were significantly (P < 0.05) higher than the corresponding values (78.53 +/- 0.98, 78.67 +/- 0.58 and 88.23 +/- 0.47%, respectively), recorded during the cold-dry season. In conclusion, the hot-dry season induced heat stress in the donkeys, resulting in a decrease in time spent on feeding and oxidative stress, as evidenced by high erythrocyte MDA concentration and percentage haemolysis.