The use of milk progesterone and electronic vaginal probes as aids in large dairy herd reproductive management

In a large herd 427 cows were examined for reproductive condition 26 to 34 days after calving. Progesterone profiles were obtained from a total of over 5000 milk samples which were taken twice weekly for 4 weeks, starting at the time of examination, and again 21, 23, and 25 days later. Researchers lived on the farm during the experiment to sample cows and record all data. Electronic probe measurements of cervical-vaginal mucus also were obtained. All cows were inseminated artificially with frozen semen from one organization. Eleven percent of the cows were not inseminated in the estrual phase as determined by substantial concentrations of progesterone in milk (MP), and 2% were pregnant and aborted following insemination. The MP 23 to 25 days after insemination essentially was 100% accurate in predicting nonpregnancy and was preferable to day 21. When used in conjunction with MP on the day of insemination pregnancy prediction 23 to 25 days after insemination was 84% accurate. Non-return rate 60 days after insemination was 7% higher than palpated pregnancy rate. The use of electronic probes under large herd conditions was labor intensive and did not give repeatably distinctive values at estrus.