Dear of troy: eating dirt can sometimes have surprising benefits. About thirty years ago, my son-in-law on PEI built a new barn with cement floor, and moved his pigs into it. Not long after doing it, he noticed he was having young pigs die mysteriously. When he took them for autopsy at goverment vet labs, they had peculiary heart and liver lesions. It eventually was learned that this was due to selenium deficiency, which had only recently been recognized, because previously it was not possible to measure the tiny amounts of selenium that are essential.
If he had known, just dumping some soil onto cement floors would have kept it from happening. At that time it was not possible to control proper seleniu;m levels in feed. I guess that is no longer a problem. For humans, eating potato skins could be a valuable protection against selenium deficiency.