A heat exchanger header includes a primary fluid duct extending between a fluid port and a first branched region, a plurality of secondary fluid ducts fluidly connected to the primary fluid duct at the first branched region, wherein an overhang region is formed laterally between adjacent ones of the plurality of secondary fluid ducts, and wherein each of the plurality of secondary fluid ducts extends between the first branched region and a second branched region, a plurality of tertiary fluid ducts fluidly connected to each of the plurality of secondary fluid ducts at the second branched regions, a primary horn integrally formed with and extending from the overhang region, an at least one secondary horn integrally formed with and extending from one of the plurality of tertiary fluid ducts, and a sacrificial support structure extending between the primary horn and the at least one secondary horn.