Dr Gretchen M. Hill, from Michigan State University (USA), reviewed trace minerals at the animal and cell levels. Zinc ions are absorbed at the brush border membrane by intestinal transporters ZIP, and released by ZnT transporters in the bloodstream, where they will be primarily carried by albumin. Iron intestinal absorption is also tightly regulated through Divalent Metal Transporter (DMT1), then present in plasma transferrin and in red blood cells hemoglobin. Like iron, copper has two oxidation states. Monovalent copper will enter into the enterocytes by CTR1 (and DMT1) transporters, and will be pumped out from the basolateral membrane by ATP7A protein. Synthetised in the liver, ceruloplasmin carries 90% of Cu in the blood. Trace minerals are absorbed in the proximal part of the small intestine. Duodenum is approximately 1m long, but jejunum is more than 15m long. So jejunum represents 90% of the total length of the small intestine of the adult pig.