I’d like to share some thoughts inspired by the column discussing PETA’s campaign against the raising of dairy animals. I apologize for the somewhat techinical tone of my prose. Perhaps someone who is a better writer would like to amplify.
At its best, the relationship between humans and their domestic animals is a form of symbiosis, in which two species have a relationship that benefits both of them, in fact usually is vital to them. Domestic animals could not well survive without human care, and traditional dairy-farming cultures could not well survive without the contribution milk makes to their diet.
Imagine a wild cow, at risk from predators, infected by parasites, sometimes going hungry – in sum, living a life that may be brutal and short. Now imagine a domestic cow, ideally well treated: always fed, given veterinary care, placid and secure. Sharing some of her milk with humans is a small price to pay for such benefits, if she is allowed to raise her calves to adulthood and the humans only take the surplus milk. Apart from issues of the cow’s subjective comfort, such an arrangement greatly improves her chances of leaving many healthy offspring, the only evolutionary justification for symbiotic relationships.
Domestic cows produce more milk than their wild counterparts would. This is a fine example of the kind of adaptation found in many symbiotic species, where the organism has a feature with no other function than encouraging its symbiotes to stick around. One example is the bullhorn acacia tree, which grows protein-rich granules on its leaves, specifically designed to feed the ants that guard it from browsers and clear away plants that might overshadow it. So, why shouldn’t the cow produce extra milk to “pay” the humans that feed and tend her? The only drawback, from the cow’s point of view, is that producing all that milk might be a drain on her resources – but, since the domestic cow is well-fed and protected from stress, she can well afford the milk.
Therefore, there are good ethical arguments for treating dairy animals well, but none for not having them at all.