A Jafari Dehkordi - Department of Large Animal Internal Medicine, Veterinary Faculty of Shahrekord University, Shahrekord, Iran
A.N Mohebbi - Department of Veterinary Clinical Pathology, Veterinary Faculty of Shahrekord University, Shahrekord, Iran
Sh Balali Dehkordi - Graduated from the Faculty of Veterinary Medicine, Shahrekord University, Shahrekord, Iran

BACKGROUND: Cardiovascular system is a very important organ that plays a vital role in tissue function. In farm animals, the growth and high milk production depends on function of cardiovascular system. OBJECTIVES: Cardiovascular health in high and low-yielding dairy cows was investigated. METHODS: Fifty 4-year-old high- yielding Holstein dairy cows and fifty 4- year-old low- yielding Holstein dairy cows were used in this study. Electrocardiogram was recorded by a base- apex lead, andblood samples were collected from the jugular vein for the measurement of cardiac biomarkers (CK (Creatine Kinase), CKMB (Creatine Kinase-Myocardial Band), LDH (Lactate Dehydrogenase), and AST (Aspartate Aminotransferase) and troponin I). RESULTS: Cardiac dysrhythmias were detected more in low- yielding Holstein dairy cows (62%) compared to highyielding Holstein dairy cows (46%). The cardiac dysrhythmias that were observed in low- yielding Holstein dairy cows includedsinus arrhythmia (34.7%), wandering pacemaker (22.45%), sinus bradycardia (18.37%), sinus tachycardia (10.20%), atrial premature beat (2.04%), sinoatrial block (2.04%), atrial fibrillation (8.16%), and atrial tachycardia (2.04%). The cardiac dysrhythmias were observed in high- yielding Holstein dairy cows, including sinus arrhythmia (86.95%) and wandering pace maker (13.05%). Also, notched P wave was observed in highand low- yielding Holstein dairy cows, 30% and 14% respectively. The amount of cardiac biomarkers in the low yielding cows was significantly higher than that of the high yielding cows. Further more, there was not any detectablesignificant difference of serum concentration of total CK between the high and low- yielding Holstein cows. CONCLUSIONS: Despite significant differences in cardiac biomarkers and based on the normal range of cardiac biomarkers in both groups, the increase in cardiac dysrhythmias in low- yielding Holstein dairy cows may be metabolic and electrolyte disorders.

dairy cows, dysrhythmias,myocardial biomarkers