I think it's important to consider the inputs. Carnivorism is just herbivorism with more overhead. Perhaps I do need to eat ~3 times the non-heme iron to get the same level of absorption, but plant crops usually win out over cattle when it comes to scalability.
Is plant iron more bioavailable to cattle animals than humans? That might tip things slightly in favor of carnivorism, however cattle does a lot more than just convert non-heme iron to heme iron and facilitating that excess resource usage may be more trouble than the heme iron is worth.
Is plant iron more bioavailable to cattle animals than humans? That might tip things slightly in favor of carnivorism, however cattle does a lot more than just convert non-heme iron to heme iron and facilitating that excess resource usage may be more trouble than the heme iron is worth.