I grew up in the Texas panhandle and worked on the big ranches as a kid: 6666 @ Panhandle; Johnson's @ Borger, etc., plus, neighbored at most of the others. There are literally thousands of pipe cattle guards up there as the oil companies installed them so their pumpers wouldn't have to open and shut a hundred gates a day, or be accused of leaving one down and letting cattle out. I never knew of a cow getting out over one, or even heard such a story. Maybe north Texas cattle are just dumber than most, I don't know. We DID train our horses to jump over them so we wouldn't have to get down and open a wire gap, but then some horses learned to get by them on their own, and you never used a cattle guard on the horse trap, anyway. Nowdays, people who already have them on the outside fences are putting chains or even swinging pipe barricades on them - not to keep cattle in, but to keep cars out.