Thanks to tools, I'm a far more capable hunter than my cat. It's trivial for a human of any size to kill a slow moving cow. It's very hard to imagine any scenario where a domestic cat would be capable of hurting a cow, let alone kill and eat it.

Humans have been hunting prey many times larger than themselves for tens of thousands, if not hundreds of thousands of years (maybe even millions).

Actually I'm well north of 100kg, and being a tool-using ape that's about 1/6th the weight of and considerably taller than the animal I want to eat it's a fairly easy task.

If I was 1/150th the weight of a cow with my eyeline roughly level with the top of the animal's foot, armed with teeth about 12mm long and sharp claws about 5mm long, I suspect it would be considerably more difficult.