Well, sure. But you can still strive to give them the things that are known to make them more happy than not. Also, pigs are not plagued by the same level of human emotional baggage and potential for enui as you and I. A pig isn't going to look at the lettuce you give him and wish he had ordered a nice slice of cucumber instead, and wonder about how the other pigs are judging his caloric intake, and think about whether it is locally grown or the pigs in other countries who might not have lettuce, or the rich pigs who get better lettuce; he's not going to be distracted by problems at work, or thoughts of that girl he saw on the subway; he won't fret about the cost of the lettuce, or be transported back to a moment from his childhood when his parents bickered over their lettuce dinner. Instead, the pig will feel safe and less anxious because his basic needs are being met, and as those with knowledge and experience can tell you (and have told you), having a friend is one of those basic needs.