Have had many of these cases over the years. You don't need much of a depression in the ground. Odds are greater than 1 in 1000. It is a heritable condition, based on a certain phenotype. I say this because I had 3 maternal sisters all die doing the same thing over a 2-3 period. Typically fast-growing heifers (i.e. 1200 lb yearling weight) that are wide-hipped and lots of spring of rib are the most susceptible, when heavy in calf. Old broad-backed cows heavy in calf will do it to. You have about 20-30 minutes to upright them, before its game over. :cowboy: