They've always had a "feeding" sub-plot for majority of the seasons... Season 2 had Hershel and his family feed the people in the barn and in season 3 it had the Governor feeding his daughter albeit for personal reasons. Who knows how this mystery person's reason is :/
Also, it was clear that the pigs carried some sort of disease on them (something like a swine flu) and thats what resorted partly to ricks decision of sacrificing the pigs and also burning the pigsty down along with his clothes that had the blood on it.
As for the burning of the "diseased", it's really up in the air as to who it is. I don't really see anyone of the recurring cast doing it and it's more than likely a guy due to the fact that the bodies were physically dragged quite a long way to the back and there were two of them, not a feat that I see any of the female characters being able to pull of (apart from maybe Michonne) I suspect it was that guy who knocked over the alcohol cabinet in the first episode since they are seemingly trying to make him important that or it could be "Doctor S." who was briefly seen in this episode, he has a medical background so him "studying" the zombies can't be out of the picture and him being well versed in his field, could have burnt the diseased people himself to stop the spread.
