This study was carried out on 36 lambs in private farm at Dakahlia governorate, 7 of them apparently healthy, 11 clinically diseased suffering from respiratory affections and 18 slaughtered lambs. Bacteriological examination of the samples revealed that 35 samples were positive for bacterial isolates, distributed as 6 (85.71%), 11 (100.00%) and 18 (100.00%) of apparently healthy, clinically diseased and slaughtered lambs respectively. 66 bacterial isolates identified biochemically into P. multocida 19 (28.79%), P. heamolytica 5 (7.58%), E. coli 15 (22.73%), Klebsiella pneumonia 8 (12.12%), Pseudomonas aeruginosa 7 (10.61 %) and staph. aureus 12 (18.18%). Pathogenicity test for P. multocida isolates indicated that all isolates were pathogenic. Blood samples were collected from the clinically  healthy and diseased groups of lambs. Two blood samples were obtained from each animal, one as a whole blood and the other in the form of blood for obtaining clear non-haemolysed serum. Haematological studies revealed that presence of high significant decrease in the total erythrocytic count, haemoglobin concentration, packed cell volume and blood lymphocytes (per mm³ blood) in diseased animals when compared with clinically healthy ones. Also high significant increase in total leucocytic count, significant increase in neutrophil, oesinophil and monocyte cells were recorded in diseased cases.The studied biochemical parameters revealed high significant elevation in the values of AST, ALT, GGT and blood urea in diseased animals. Also creatinine showed marked elevation. Presence of high significant decrease in the level of albumin, while  total protein, sodium chlorides and calcium levels were significantly decreased. On contrary, presence of significant increase in the glucose and potassium levels. From previously mentioned data, it was cleared that respiratory affections in lambs especially those of bacterial origin cause significant changes in blood picture, liver and kidney functions and the level of both sodium, potassium, chloride and calcium.