Stretching the Vulva.
After it has been determined that there is enough room for the calf to be delivered per vaginam, it is helpful to stretch the lips of the vulva, especially in heifers. With the heifer standing, the forearms are inserted halfway to the elbows. Next, with the fingers folded, the arms are wedged apart in the direction from 11 o'clock to 5 o'clock and alternately from 7 o'clock to 1 o'clock, for 10 or more repetitions. After this the heifer is cast and the calf is extracted.
Haibel GK (1983)