Coldfront, geez! now you asking... seeing as you have a great bait line yourself lol!
But my 2c worth, I use brown sugar in my ground feed.
I have been experimenting with salt too, but Ive found rock salt to be the best, dont ask me why, maybe the iodated process in table salt has something to do with it.
The salt I'm currently using is SAXA rock salt, found at PnP, its for grinding, but disolves ok with the feed.
Amount? I salt to taste, as if you were cooking for yourself.(maybe the salt releases more of the baits flavour?)(the feed also seems softer when cooked)
It may also have something to do with a missing mineral the fish need, I know my koi fish require 3kg rock salt per 1000 liters water, but this is to generate a thicker slim coat over their scales so parasites, bacteria and viral infections cant enter as easily.Ive noticed they more agile, and their appetites pick up more when the water is salted.
I dont think the amount Im using in my feed could ever be the case with Carp in a dam, but, just wanted to illustrate that carp dont mind salt in the water.