The incidence of abomasal mucosal diseases in dairy cows suffering from gastrointestinal disorders is becoming more frequent in modern intensive production. Clinical signs are often non-specific. In this study, 67 dairy cows with gastrointestinal disorders and 9 healthy dairy cows as the control group were used. In order to make a tentative diagnosis, a complete physical examination was performed, and the fecal samples were taken from each cow for the fecal occult blood (FOB) and the fecal egg count (FEC). Blood samples were taken from the coccygeal vein for WBC, Hematocrit (PCV) evaluations, and serum biochemical analysis. Serum pepsinogen activity and total protein; albumin and globulin were measured using validated standard methods. The statistical analysis was performed using SPSS software. The level of significance was set at P<0.05. A significant increase in serum pepsinogen activity was seen in all the cases of abomasal displacements compared to the control group. Among the abomasal displacement groups a significant increase in serum pepsinogen activity was seen in abomasal displacements with suspected abomasal ulcer in comparison with those without any signs of abomasal ulcer (positive FOB and melena). No considerable differences were observed between WBC, PCV, and total protein and globulin in different gastrointestinal disorders and the control group. In this study, the serum pepsinogen activity in all dairy cows with signs of abomasal ulcer (melena and positive fecal occult blood test) was higher than the control group, since all of the cases had negative abomasal parasites; these increases in the signs of abomasal ulcer could predict abomasal ulcer complication in the cases of displacements.