The amount of a alpha-1,3-mannosyl-glycoprotein 2-beta-N-acetylglucosaminyltransferase when measured in blood serum. The trait is Ontology of Biological Attributes term OBA_2042356 (level of alpha-1,3-mannosyl-glycoprotein 2-beta-N-acetylglucosaminyltransferase in blood serum). Also known as: blood serum alpha-1,3-mannosyl-glycoprotein 2-beta-N-acetylglucosaminyltransferase amount.