Changes of the Electrocardiographic Parameters during Aging in Clinically Healthy Holstein Cattle

Electrocardiograms were recorded from 89 clinically healthy Holstein cattle divided into 10 age groups, comprising newborn calves (18 to 72 hours), 15 days, 1, 3, 6 and 9 months and 1, 3, 5, and 7 years of age. The electrocardiograms were recorded on a bipolar base apex lead, using limb lead I. Duration and amplitude of the P, QRS complexes, T waves and the PR, RR, QT and ST intervals were measured in traced electrocardiograms. The values of P-duration, P-R, R-R, Q-T and S-T intervals in adults were significantly higher than young cattle, but the amount of P and R-amplitudes in older animals were significantly lower than younger once (P<0.05). There were no significant changing patterns of T-duration, T, S and Q-amplitude among all age groups. With advancing age, degenerative changes such as developing fibrous tissue and fat deposits occured in heart muscle and its conduction system. Furthermore, the conductive properties of the body, cardiac mass and size, characteristics of Purkinje fibres in cardiac conductive system and changes of vagal tone during aging can explain the changing patterns of bovine electrocardiographic parameters at different ages. The present study, also, incorporated both calves and adult Holstein cows in a single wide study which can provide a good basis for judging the electrocardiograms in cattle.