I'm going to have to go with bear on this one, WB. If you check Snopes you will find out that the commonly held definition of lowing is nothing more than an ancient urban legend gone horribly wrong and has resulted in a misconception that, with centuries of usage, has become accepted as fact.
Along with more common varieties of cattle here in Northern California, we have two special breeds known as Dutch Belted and Belted Galloway. These cattle have been raised specifically for their inherent love of lowing and are trained and exported to areas that have an appropriate level of annual snowfall. They, in turn, train other breeds upon their arrival.
Few know of this process, as can be noted in bear's post, but it has been a secret and benevolent partnering of man and beast in NorCal for decades. Sonoma County, known for such significant residents as Luther Burbank and Charles Shultz, has funded this project solely for the purpose of maintaining the art of lowing so that this tradition, such an integral part of the rich bovine culture throughout the ages, will not be forever lost.
Training begins early
This dedicated mother begins training her calf shortly after birth. This new baby is being carefully taught the first step in the specific art of 'Oreoing". In it, the cow must learn to completely tuck all four limbs, as well as the tail, under the body. The result, when performed properly in a snowy field, is a stunning display that looks as though such a cookie being dunked in milk. It is few herds who have successfully learned to do this particular manuever to perfection, but there are reports that it does happen on occasion. The resulting performance is breathtaking.
Practice, practice, practice
As the belted cattle grow to maturity, they must practice often as is the case with any craft. They may be seen, at times, going through the drills for a variety of lowing techniques, both in the barn and out in the field. They are particularly fond of practicing on beds of clover or mustard flowers.

It is rare that one is able to get a photograph of a cow actually going into a lowing dress rehearsal. There is only one dress rehearsal before the cattle are shipped to the appropriate areas. This photograph was snapped just as rehearsal was beginning. Note the position of the three standing cows. Someone had leaked information to the photographer, and rumor has it that it was the cow farthest from the camera.
Some have asked why cows do lowing. It has been quietly studied here, and there are only three answers that I am at liberty to share with you:
1. Cows enjoy the brisk chill of the snow on their udders.
2. Calves are very fond of ice cream.
3. They like watching the show.