The cow whisperer

Cows only produce milk when they give birth to a calf, every 13 months or so, making the timing of reproduction a crucial part of running a dairy farm. But determining when a heifer is in heat - and when the costly procedure of artificial insemination is most likely to work - is a major chore. Farmers use different approaches for pinpointing that right moment, but none are very precise. (For more on milk and dairy farming, see What's in your milk?) "In practice, detection rates are usually less than sixty percent," says dairy scientist Gary Rogers from the University of Tennessee. "Simple visual monitoring by experienced farm hands still works best, but that gets expensive on our big dairy farms. There is a real need for a reliable, automated way to determine when the animals are in heat."

Sch?n thinks he may have found just such a method, which he published in the January 2007 Journal of Dairy Science. He has noticed that cows' vocalizations change over time, and those changes may be timed to periods in their estrous cycle. "There is the pleasant, harmonic moooooh, and a noisy, deep throated brrrrrrrr," he says, doing a great rendering of both. To investigate what those sounds could mean, Sch?n hung microphones on posts next to 10 tethered holsteins and recorded their vocalizations in the days before, during and after estrus. He found a significant change in both quantity and quality of the vocalizations as the animals went through their cycle. Vocalization rates increased 84% as the heifers approached their fertile period. Acoustic analyses revealed that harmonic "moohs," the mellow sound people usually associate with cows, decrease during heat while nonharmonic bellows, which sound noisy and grating, increased. In theory, cows could essentially tell farmers when they are ready to be inseminated.

Still, it will be some time until this technology can be put to use down on the farm. Sch?n is currently repeating the study with more cows and over longer periods of time. In the meantime, one of his PhD students is doing the same work with untethered animals, which more closely simulates conditions in herds. So far, she's found that cows generally moo and bellow less often when they roam free, but the changes at estrus are still statistically significant.

Rogers is optimistic that acoustic signals, especially when used in combination with other parameters, could help farmers pinpoint when cows are most fertile. Sch?n and five colleagues, meanwhile, have teamed up with technologists to develop a contraption, consisting of both a pedometer (cows start getting restless and move around more when they are in heat) and a microphone, which the animals could wear around their neck. Rogers, who edits the Journal of Dairy Science, thinks that using two parameters, movement and vocalization, should pinpoint the heifers' fertile days quite accurately, but, he adds, "studies with more animals are necessary to prove the concept."

Questions remain, agrees Sch?n. For instance, cows like to "rub up against each other," he says. The team will have to ensure that a microphone primarily records the vocalizations of the monitored individual, not the moos and bellows of its buddies, says Sch?n.