Reproductive characteristics of Holstein heifers fitted with intravaginal temperature transmitters.

In this experiment, the safety and feasibility of intravaginal temperature transmittance were tested by radio-telemetry. Each transmitter was positioned non-surgically with a plastic anchor. Heifers wore these transmitters for 107 days with no apparent physical or physiological effect. While the transmitters remained in place, estrous cycles, estrous behavior and fertility following artificial insemination were normal. The data usually revealed a temperature spike of one day on the day of standing heat. Time series analysis enabled the identification of significant temperature departures where the base line was a changing value due to seasonal adjustments. The temperature increase measured at 0645 h was about 0.5 degrees C above the previous five-day average. Absence of 21+/-3-day cyclicity in temperature spikes for two heifers revealed their cystic ovary condition which was later confirmed by rectal palpation. Progesterone and estradiol-17beta patterns were normal for all but one of these heifers. Prostaglandin F2 proportional-induced estrous behavior lacked the expected temperature spike. Affected heifers usually continued to have their temperature spike one more time at a regular estrous interval from the spike prior to PGF2 proportional injection.