Reply To: GMOs linked to 3rd generation sterility, yet OU says they are Kosher, why?

Re your question about the theoretical hybrid pig/cow, to explain what Mentsch was referring to:
if one would discover a new breed of cows, even though it has the signs of a kosher animal, we could not automatically eat it, since our Rabbanim have established an additional criteria – that there is a tradition (mesora) that the animal is kosher. Without that mesora, we cannot eat it. These are real questions that have come up from time to time. Since your new hybrid obviously cannot have had a mesora establishing it as a kosher animal, we cannot eat it. In this way animals are different from plant products.