Short communication: an electronic probe versus milk progesterone as aids for reproductive management of small dairy herds.

A simple probe especially designed to take electrical resistance measurements at different positions in the anterior vagina of a cow was compared with milk progesterone determinations on 108 cows. Milk samples were taken 3 x weekly, 21 to 60 d postpartum, at the time of insemination, and 21 to 23 d later. Electrical resistance measurements were made on a similar schedule. In 10 other herds, 187 cows had only milk samples taken. No cows with high milk progesterone values became pregnant when inseminated, but the electrical resistance values were less accurate in designating which cows were suitable or unsuitable for insemination. Both low milk progesterone and low electrical resistance values 21 to 23 d after insemination provided an early and accurate indication of a need for reinsemination. These indicators were consistent with 94 to 100% of these cows being diagnosed as not pregnant 6 to 8 wk later. Daily probing, starting about 19 d after a previous insemination, could serve as an early check of pregnancy and assist in identifying cows for immediate reinsemination.