RESUMO
Short-term electrocardiography is one of the most suitable tools to study the electrical activity of the heart, but the use of a tool such as a Holter-monitor with the ability to assess the long-term of the heart electrical activity, can provide more accurate information about these activities by comparing the results. It is possible to understand the superiority of each over the other and the resulting differences. Therefore, 60 female Holstein cows in 10 age groups, including 1 day, 1, 3, 6 months, 1, 2, 3, 4, 6 and 8 years were included in the study (6 heads in each age group). Electrocardiography (for 5 min) and Holter-monitoring (for 24 hr) were performed from the entire study population. The Q, R and T amplitudes in electrocardiography were significantly higher than those in Holter-monitoring. The P, R and T durations and P-R, R-R, Q-T and S-T intervals at all ages were significantly longer in the Holter-monitoring than in the electrocardiographic method. The heart rate of animals was significantly lower in the 24-hr Holter-monitoring than in the short-term electrocardiography. The trend of changes of all parameters was significant during ageing. Cardiac arrhythmias included sinus arrhythmia and sino-atrial block, which were the most common cardiac arrhythmias in the 24-hr Holter-monitoring. It appears that long-term Holter-monitoring is a more reliable method than short-term electrocardiography to assess cardiac arrhythmias. Additionally, the indicators of electrical activity of the heart (waves) in the Holter-monitoring method are significantly different from short-term electrocardiography, which is probably due to the collection of information over a long period and in non-stressful situations. Furthermore, it appears that the use of the 24-hr Holter-monitoring method is preferable to the short-term electrocardiography method to evaluate the electrical activity of the heart of cows at all ages.