Vaginal temperatures of 20 pregnant dairy cows were continuously recorded using data loggers with built in temperature sensors for 3 weeks. Plastic anchors were designed and produced to hold data loggers inside the vagina of cows. The anchors were manufactured from plastisol - a flexible translucent plastic that could be molded to a desired configuration. The material is contact compatible with dairy products but is not known if it qualifies for a long-term implant. The plastic cures by heating to 160°C, which takes about one hour in an oven at a temperature of 215°C. The volume of material necessary to produce one anchor is about 90 cc. The system and procedure was reliable, accurate, low cost, easy to implant and does not fall out, and had no ill effects to the health of the cows or disturb their behavior/activities. Rectal temperatures were recorded using a high performance digital thermometer. The vaginal temperatures were compared to the rectal temperatures and the results matched to within 0.06 ± 0.015°C.