Here is my source for the breakdown of $200 million in Northern "exports" to the South, and here it is again in table format.
Curiously, except for smoked fish there are no food items on the list, and I'm not sure what that means.
I've supposed it means that most of the food items "imported" by, say, the Deep South came from Upper South & Border States.
I found an article on JSTOR titled The Antebellum South: What Probably Was and What Should Have Been by Stanley L. Engerman. Much of the piece discusses problems that the author has with previous work on the topic, and discussions of the efficiency of Southern farms and the affects of slavery on agriculture. The author also states that obtaining hard miners is difficult because no records remain from distribution by certain means such flatboat shipments and overland trade.
However, he does state that at least parts of the South were “deficit areas in grain.” Apparently 1860 was a bad year for grain production in at least parts of the South. He also writes “That’s why the possibility of regional self-sufficiency is indicated by the “better estimates,” they remain substantial room for interregional flows in both types of commodities (as well as in livestock on the hoof.”
So I think it’s highly likely that at least some of the food consumed by both the Southern population and its livestock came from areas outside the Southern and border states.
Perhaps more interesting though is this line:
“Regional distributions of federal receipts and expenditures by John Legler indicate that in most antebellum years federal expenditures in the south exceeded revenues collected from that region.”
Hmmm....