The amount of a alpha-1,3-mannosyl-glycoprotein 4-beta-N-acetylglucosaminyltransferase C when measured in blood serum. The trait is level of alpha-1,3-mannosyl-glycoprotein 4-beta-N-acetylglucosaminyltransferase C in blood serum (OBA_2042361). Also known as: blood serum alpha-1,3-mannosyl-glycoprotein 4-beta-N-acetylglucosaminyltransferase C amount.