I've often asked myself the same question, out of all the things...."why cows?"

As another member had claimed, cattle DNA is somewhat similar to that of humans, which can be a good explaination, but still....

Humans, up until recently, harvested equine estrogen for use in hormone therapy and this has very little to do with any similarity if a horse's DNA to that of a humans. It has more to do with the chemical similarity to that of human estrogen.

There are features that are unique to the specific tissues that have been removed from "genuine" cases of "cattle mutilation". Evidently whomever or whatever is using laser scalpels to remove certain organ tissue from these cattle are after a specific group of hormonal chemicals. This specific group fo chemicals occurs in high concentrations in cows and less so in other species. This is why cattle.

I don't want to be the one to start the rumor that aliens are organic androids made from live (but not for long) cows.
So I won't.

Birds and many other different types of animals were mutilated similar to cattle including humans. But why cattle was their main choice is because cattle are probably the easiest. Think if you had an underground base near the 4 corners US and you went out to explore the new world, the first thing you would probably see in the rural areas is cattle.

The overall point was for creating hybrids, exactly the same as the abductions. They have vats of formula to feed the hybrids containing [human/animal blood] plasma, deoxyhemoglobin, albumin, lysozyme, cation, amniotic fluid and more.

There is no reason to associate religion with these aliens.