up in Alberta they are referred to as "Texas gates"

awarded to zvbxrpl for the proper plural of beef.

So, talking to someone from out west years ago, they explained that once a cow has experienced a real cattle guard (as shown in the Shorpy pic)--ya can just PAINT them on the road, and they work just as well. See below. The beeves come gamboling down the highway, and when they see the painted lines, they're like 'whoa, whoa, whoa! Stop! Can't cross THAT!' Explaining, I guess, the lack of bovine Nobel Prize winners.

Cattle guards probably worked well from April to November at discouraging herds from trying to hoof it across the opening in the fence line, but one good heavy snow would fill in the gaps between the bars, thereby making it more tempting to trot out. Restoring its effectiveness in winter as an obstacle was probably a cowboy's unpopular chore.