Well maybe it is because a symbiotic relationship would need tonsomewhat benefit both parties. In this relationship we are more of a cruel and sadistic parasite, just waiting for the best moment to kill (when profit and taste is at its best). But no, i guess being forcefully impregnated, seperated from offspring and milked until your are unprofitable is a symbiotic relationship in your mind. As a thanks for service these cows get killed after half of their live span. But hey atleast they get much more than our beloved meat live stock. You should also look how naturally these cows and their udders have ‘’''evolved"" in the last hundred years. Much more cruel than what has been done to pugs (not that this is fine). The same goes for hens (for eggs) and the absurd amount of breast muscle chickenbreeds have.