Cardiac troponin I (cTnI) is known to be a sensitive cardio biomarker to determine the myocardial damage in diseases affecting the cardiac muscles. However, there has not been sufficient research about cTnI concentration, which is the most sensitive indicator of myocardial damage in sheep with acute ruminal lactic acidosis (ARLA). For this reason this study aimed to evaluate the serum cTn1 concentration in sheep with ARLA. Those diagnosed with ARLA (n = 20) from the total of 40 Akkaraman (White karaman) sheep, aged between 1-2 years used in this study comprised the affected group and the healthy ones (n = 20) comprised the control group. Ruminal fluid was obtained from the animals from both groups with the help of a stomach tube, and examined immediately. Blood samples were taken from the jugular vein of the sheep and the serum was separated. Serum cTnI concentration was measured with a commercial immunoassay system, using the one-step sandwich method. Serum enzyme (ALT, AST, CK-MB and LDH) activities were determined via a clinical biochemistry autoanalyzer. The average serum cTnI concentration was at the level of 0.035 +/- 0.015 ng/mL (range; 0.02-0.06 ng/mL) in the control group sheep. It was determined that there was a substantial increase in the group with ARLA and the average concentration reached the level of 0.103 +/- 0.080 ng/mL (range; 0.03-1.7 ng/mL) (P<0.0001). It was observed that another cardio marker, CK-MB, was found in the group with ARLA 454.50 +/- 191.88 U/L (range; 214-861 U/L) and increased in comparison with the control group 224.35 +/- 83.33 U/L (range; 133-421 U/L) (P<0.0001). An increase in LDH (P<0.001) and AST (P<0.001) from liver enzymes in the group with ARLA and ALT activities compared to the control group was identified (P<0.01). In conclusion, this present study determined that the serum cTnI concentration was high in sheep with ARLA and it was concluded that it could be useful to evaluate cTnI concentration as an important marker to determine the prognosis in sheep with ARLA.