I wonder if anyone has ever tried to milk seals and/or whales. Their milk is around 50% fat (compared to 4% for whole cow's milk). You could get more butter out of it. In the case of endangered species, farming them might be a way to save them. The biggest problem is finding a suitable enclosure.
Guinan: "Consider that in the history of many worlds there have always been disposable creatures. They do the dirty work. They do the work that no one else wants to do, because it's too difficult or too hazardous. And an army of milk seals, all disposable? You don't have to think about their welfare; you don't think about how they feel. Whole generations of disposable seals."
Picard: "You're talking about slavery."
Guinan: [prodding him on]: "I think that's a little harsh."
Picard: "I don't think that's a little harsh, I think that's the truth. But that's a truth that we have obscured behind a... comfortable, easy euphemism. 'Milk production'. But that's not the issue at all, is it?"
-- Star Trek: The Next Generation, The Measure of a Man, 2.09