Changes in Electrocardiographic Parameters with Growth in Holstein Cows

Changes in electrocardiographic measurements were studied in growing Holstein cows. These cows, including neonatal and 12-year-old ones, were kept on the Stock Farm, Faculty of Agriculture, University of Tokyo. Electrocardiograms were recorded in the A-B bipolar lead and the standard limb lead. Those recorded in the A-B lead were used to measure the intervals of RR, PQ and QT, the durations of P, QRS and T waves, and the amplitudes of P, QRS and T waves. The mean electrical axis of the QRS complex was calculated from those recorded in the limb lead. The results obtained are summarized as follows. 1) The RR, PQ and QT intervals and the P and QRS durations increased with growth. 2) No changes were observed in P wave amplitude with age. The amplitude of the R wave was rather high till 30 days of age. The wave form of the QRS complex was of rS type. Afterward, it shifted to the QS type with no R wave. The amplitude of the S wave decreased gradually until 3 or 4 months of age. It was stabilized in about 0.8 mV. The amplitude of the T wave was fluctuated from 0 to 0.5 mV through all the stages. 3) The mean electrical axis of the QRS complex changed with age. The QRS vector axis was oriented forward to the left till 100 or 200 days of age. After that, it was oriented backward to the left. 4) Prolongation of PQ and QT intervals and forward deviation of the QRS vector axis were observed in cows of over the 4th calving. 有蹄類の心電図は霊長類,食 肉類の心電図 に比べて 著 しく異な った特徴 がみ られる。そのた め比較 生物学 的観点 か ら,ウ シの心 電図の特徴 な らび に誘導 法に関 す る研究は多数行なわれてい る 。 心電図 は心臓循 環系 検索の重要 な手段で あるが,心 電 図学 的正常値 は 成長 に ともな って変化す るか ら,動 物種 ご とにこれ を