I'm not buying the helicopter theory. You just don't see or hear helicopters crossing over farms very often, and they'd have to cross quite a bit of farmland to get where cows are generally kept. When farmers hear a chopper, they investigate immediately because they assume it's there for a reason, and it's probably not good. That would be especially alarming at night.
When a cow falls, it falls really hard. They can break ribs, hips and legs in a fall. That's why dairymen put so much time into keeping all the smooth surfaces that cows have to walk on as slip-proof as possible. They're hosing these surfaces down all the time, and tossing straw or sand on them. Just a tiny crack in the hoof can cause a cow to die from an infection that started in its foot.
These are beef cattle operations. Some ranches in the western US consist of 100s of thousands of acres. It takes many acres of scrub land to feed one animal. They also have grazing permits and run their cattle on thousands of acres of BLM land in the summer before they are rounded up in the fall and brought back to ranch property. So, it doesn't seem odd to me that a helicopter could be flying around at night and no one would see it. These huge ranches have their own helicopters.
Most of these articles don't give a very good description of the location, as to ranch land, BLM land, Forest Service land or where exactly they were found and how long they may have been dead when located.
On a large ranch cattle may not see a human for months. Just like the old days the cowboys herd them to their summer pasture and go back and get them in the fall. There may be a trip or two to check on them but mostly they do well on their own.