An electronic nose to detect changes in perineal odors associated with estrus in the cow.

Changes in perineal odor as estrus is approached could form the basis of a new method of estrus detection. Perineal odor of cyclic cows was monitored. Estrus was identified using ovarian ultrasound, behavioral observations, and plasma assay for progesterone and estradiol. Samples were taken from the dorsal lateral perineal (perivulval) area using cotton bud swabs and presented to an electronic nose. Twelve conducting polymer sensors were used to quantify odor in terms of a change in sensor resistance. Preliminary data (Experiment 1) indicate that the odor signals between the luteal phase and estrus could be distinguished for a group of five cows. In Experiment 2, samples were obtained daily from eight cows during the midluteal phase and from d -2 to d 8 of the cycle (d 0 = day of estrus, induced using cloprostenol). Seven of the eight cows cycled normally. Of the 12 sensors, 7 showed a significant change in resistance that was dependent on the day of the estrous cycle. Basal values were those taken in the luteal phase; values peaked on d -1, rose transiently on d 3, and returned to baseline on d 5 to 6. This pattern is strongly correlated with plasma estradiol concentration. The use of artificial olfaction could enable more accurate detection of estrus and has the potential to increase fertility in cows.