Why is lard not allowed? What difference is it from having milk or butter on an abstinence day?
Good point. Milk or butter contain the fat of the cow, albeit in mutated form. Lard is just a clarified form of animal fat (and sows do give milk, though I've never had the pleasure).
Side point, in her final days, my mother recalled that she was given goat milk as a child when she was sick, and I asked her if she'd like to get me some goat milk for her to drink, as she was only able to take liquid and pureed nutrition --- when she rallied one night, she asked for beer and pizza, which I indulged, but aside from that, it was pretty much just pudding, mashed potatoes, coffee, and so on. The end came before I was able to track down some goat milk for her.
Requiescat in pace.