Abstract: This study was conducted on 55 dairy and dry cows with signs of Sub-Optimal Performance (SOP) to determine the relationship between serum mineral status and SOP. The herd was subjected to some changes such as renovation of mangers, rationing and removal of short comings as; dry matter and roughage deficiency. Jugular blood vein was collected before changes to management of the herd and in a 3-4 month period as the second and the third sampling. Serum calcium, sodium, potassium, magnesium, manganese, cobalt, copper, iron, zinc, phosphorous, chlorine and ceruloplasmin concentrations were measured for each blood sampling time. There was significant differences (p<0.05) between serum mineral concentrations and reference values before exercising the changes to the management of the herd. There was an incremental improvement (p<0.05) in the serum mineral concentrations and performance during the blood sampling times. The present study indicates that serum mineral status may be a valuable indicator of animal or herd status and worth watching when considering animal welfare and herd profit.