The maternal rats at preconception and five to six pups from each group at postnatal 24 hours, 4 weeks, 8 weeks, 12 weeks, 18 weeks, 22 weeks and 26 weeks were randomly selected to detect serum retinol levels. The pups younger than 8 weeks old were decapitated to collect the blood; and the blood from the pups at the age of 8 weeks and older were collected via the caudal vein. All pups were decapitated after the last behavioral tests to detect serum retinol levels and confirm the success of the animal models. Serum retinol was measured using high performance liquid chromatography (HPLC) as previously described [31 (link)]. Briefly, 200 µl of serum was deproteinized with an equal volume of dehydrated alcohol. The retinol was extracted from the serum by adding 1,000 µl of hexane and evaporated with nitrogen gas. The retinol residue was dissolved in 100 µl of the mobile phase mixture (methanol:water=97:3). Then, 20 µl of the dissolved liquid was tested in the HPLC apparatus (DGU-20As, Shimadzu Corporation, Kyoto, Japan) on a silica column with a 315-nm ultraviolet photodiode array detector. All procedures were performed in a dark room to protect the samples from light at the Children’s Nutrition Research Center in the Children’s Hospital of Chongqing Medical University.