A documentary? Really? They have a long tradition of setting up scenes to show the view they want you to see. There is some fact behind some, but there is no requirement that they be true.

Cows don't run out of the barn in any case I've ever seen - they walk. The young calfs run out, but not the older cows. (and maybe some of the young cows). If you typical cow is running it is because she is scared.