Effects of age and season on haematological parameters of donkeys during the rainy and cold–dry seasons

The aim of the study was to investigate the effects of age and season on haematological parameters of donkeys at rest during the rainy and cold–dry seasons. Thirty healthy donkeys divided into three groups based on their age served as the subjects. During each season, blood sample was collected from each donkey thrice, 2 weeks apart, for haematological analysis, and the dry-bulb temperature (DBT), relative humidity (RH) and temperature–humidity index (THI) were obtained thrice each day during the experimental period using standard procedures. During the rainy season, the mean DBT (33.05 ± 0.49 °C), RH (73.63 ± 1.09 %) and THI (84.39 ± 0.71) were higher (P < 0.0001) than the corresponding values of 24.00 ± 0.44 °C, 36.80 ± 0.92 % and 64.80 ± 0.62, during the cold–dry season. Packed cell volume (PCV), erythrocyte count [red blood cell (RBC)], haemoglobin concentration (Hb), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), platelet count (PLT), leucocyte count [white blood cell (WBC)], lymphocyte count (LYM) and neutrophil/lymphocyte ratio (N/L) were higher (P < 0.05) in adults than foals during the rainy season. The MCV, MCH, WBC, NEU, LYM and PLT of adult and yearling donkeys were higher (P < 0.05) during the rainy than the cold–dry season. The PCV, RBC, Hb, MCV, MCH, and NEU of foals were higher in the rainy than the cold–dry season. The N/L of adult and foal donkeys were higher (P < 0.05) in the rainy than in the cold–dry season. In conclusion, PCV, RBC, Hb and LYM were considerably higher in foals than yearlings or adults during the rainy season, while erythrocytic indices and platelet counts were higher in adults or yearlings than in foals in both seasons. Erythrocytic indices, PLT and N/L were higher in the rainy than the cold–dry season in adults, yearlings and foals.