Pregnancy rate in dairy cows inseminated on the basis of electronic probe measurements.

A new vaginal probe with two pairs of parallel electrodes 90 degrees apart was designed with a switching arrangement so that electrical resistance (ohms) of the dorsal and the ventral areas of the anterior vagina could be monitored separately during the estrous cycle. Three inseminators probed cows during February--April, 1977, in nine herds in stanchion barn housing. Cows not seen in estrus by 40 to 60 dyas after calving were probed every 3rd day. At each dairyman's option normal cows with a low porbe reading were inseminated. Controls consisted of cows seen in estrus by the dairyman and reported for insemination in the routine manner. The diagnosed pregnancy rate for 86 first service controls was 49% versus 52% for 58 cows not seen in estrus, but identified by low probe readings. Cows varied in electrical resistance at breeding, but the fact that pregnancy rates were equivalent in the two groups is interpreted to mean that the probe was as effective in identifying cows suitable for insemination as was visual observation of estrus by dairymen.