This study aims to assess relationships between some aspects of physiology and haematology of rams from different breeds, as well as the possible influences of environmental and climatic conditions (dry or wet seasons) on animal physiology. Eighteen purebred rams from six different breeds (Santa Inês, Bergamasca, Hampshire Down, Texel, Ilê de France and Dorper) and origins were used in two seasons in Central Brazil. Body Weight (BW), Rectal Temperature (RT) and blood parameters were measured and compared their selves between dry and wet seasons and between breeds. BW, RT, RBC (red blood cells), MCV (mean corpuscular volume), MCHC (mean corpuscular haemoglobin concentration) and TPP (total plasma protein) were highly significant (p<0.001) between different breeds. Season did not significantly (p>0.001) affect BW, RT, PCV (packed cell volume), RBC, Hb (haemoglobin) and PPT. The effect of season on breed was significant (p<0.01) for BW, PCV, RBC and Hb. Hair breeds such as Santa Inês (SI) had greater adaptability to climatic conditions in the region in comparison with other breeds and this reinforces the importance of breeding programs taken in account the characteristics expressed in the place where animal will live.