That is, I think the likeliest explanation is that people are doing this for no other purpose than for it to be noticed and wondered at.
Human motivations are weird and irrational and there is plenty of evidence that some people will go to great lengths to make themselves feel entertained, smart, superior. There’s a long tradition of bored people doing weird things just to wind everyone up from behind the scenes.
There is nothing physically unexplainable here. The scene could be created by a couple of people with a sharp knife and some experience with butchering animals.
It's kind of a dick move in any case, though. Cattle aren't cheap and killing them for no reason is just destructive.
"Cattle mutilations are up."
"the ticks can attack en masse and drain young animals of blood so quickly that they die—an execution method called exsanguination"
0: Methane, explained
edit: and then cut up for some reason...
If the govt actually wanted to collect cattle for this kind of testing, they could easily pass a law that let them take animals and pay market rate for them. I imagine this would be much cheaper and simpler than ongoing covert helicopter operations combined with the cost of the investigations that the FBI did in the '70s. It's an explanation that makes basically no sense