Studies on Biotelemetry in Domestic Animals

II. Maternal ECG, Fetal ECG and Surface EMG

Abstract

In order to measure the physiological activity of domestic animals under conditions of least restraint and stress, a miniaturized FM/FM radio transmitter was built. Tow different types of transmission system were made. The transmitter, with battery, weighed 27g and had a dimension of 32×60×11 mm. The characteristics of one transmitter (type II) were: input impedance=45KΩ, voltage gain=70db (2Hz-1KHz), minimum sensitivity=50μV, time constant=0.1 sec, carrier frequency=76-90 MHz, frequency deviation=20 KHz, battery=1.3 volts mercury cell (H-D) and continuous for about 100 hours, current consumption=0.95mA (under loading), and distance=20-30 m. Those of the other transmitter (type III) were: input impedance=500KΩ, voltage gain=65db (0.5-100 Hz), and time constant=1.5sec.
In a dairy cow, radio maternal ECG recorded with the type II transmitter by A-B lead showed a distortion on each wave, compared with that by routine A-B lead. Recorded with the type III transmitter, radio maternal ECG showed a similar pattern in P, QRS, and T waves and a slight degree of distortion in the ST segment, as compared with the routine ECG. From a horse the same results as these were obtained.
The activities of biting and tail movement were also recorded as a surface EMG with the type II transmitter. In the course of rumination, with electrodes placed on the M. masseter and the upper portion of the M. cleidooccipitalis, the surface EMG signals of redeglutition, regurgitation, and remastication were also recorded. In the remastication, a very regular burst of EMG was observed, as compared with the pattern of biting of green grass or hey. The movement of the tail in the cow could be recorded as a high-amplitude EMG burst which corresponded to each wag of the tail.
In the observation of the physiological activities in free cows against the attack of insects (mainly Tabanus) in the summer season, the radio maternal ECG and surface EMG of biting and tail movement were recorded simultaneously during about 10 hours with the type II transmitter at the distance of 30m. When the cow was protected from the attack of insects in a net room, a decrease in heart rate, prolongation of feeding time, frequent remastication, prolongation of sitting time, and no movement of the tail were observed, as compared with the cow held under exposure to insects.
From the above-mentioned experiments, the newly developed miniaturized transmitters were recognizedto be useful for obtaining some bio-physiological data in free cows as a multi-biotelemetry system.