Looks like the flush free kinds are "Inositol Hexanicotinate"So the awkward part is I have no clue which is better for chickens and ducks. Both provide B3 however to put this in layman's terms flush free niacin is a derivative of niacin. Niacin helps with LPL, flush free niacin will not, chances are you ducks and chickens and geese don't have cholesterol problems but I can be wrong. And I don't think you're giving high enough volume to create a flush effect. Since were adding it into their feed most of the time you're not going to have that flush effect ( food typically eliminate stuff itchy skin part).
I personly go with just regular niacin because flush free is technically not considered niacin but Niacinamide.
But I don't know and I'll be the first one to tell you that even though there's a difference between the two I couldn't tell you which is better for poultry.
not nicotinamide.