Effects of Maternal Nutrition and One-Carbon Metabolite Supplementation on Fetal Jejunal Morphology and Hexose Transporter Expression in Beef Cattle

The objective of this study was to evaluate the effects of maternal nutrient restriction and one-carbon metabolite (OCM) supplementation on jejunal morphology and the abundance of hexose transporters (SLC2A1, SLC2A2, SLC2A3, SLC2A5, and SLC5A1) in bovine fetal jejunum. Twenty-nine crossbred Angus beef heifers were estrus-synchronized and artificially inseminated with female-sexed semen, then randomly assigned to one of four treatments in a 2 × 2 factorial design with two main factors: nutritional plane [control (CON) vs. restricted feed intake (RES)] and OCM supplementation [without OCM (−OCM) or with OCM (+OCM)]. From day 0 to 63 of gestation, CON heifers were fed to gain 0.45 kg/d, and RES heifers were fed to lose 0.23 kg/d. After d 63, all heifers received a common diet targeting a gain of 0.45 kg/d until d 161, when they were slaughtered for tissue collection and analysis. Hexose transporter abundance was evaluated via immunofluorescence and image analysis. Restricted maternal nutrition increased (p = 0.005) fetal villous height, whereas crypt depth was influenced (p = 0.02) by maternal nutrition × OCM supplementation, with RES + OCM showing deeper crypts. Muscle layers thicknesses also tended (p ≤ 0.08) to be greater in the RES + OCM. One-carbon metabolite supplementation decreased (p < 0.003) villus and total SLC2A1 abundance and tended (p = 0.09) to interact with nutrition in the crypts, with SLC2A1 levels being lowest in the CON + OCM. Abundance of SLC2A2 was influenced (p = 0.04) by an interaction, with RES − OCM showing reduced villus and total abundance. Villus and total SLC2A3 abundance increased (p = 0.08) in RES compared to CON groups but was reduced (p < 0.0001) in crypts with OCM supplementation. Villus SLC2A5 was affected (p = 0.05) by an interaction, being greatest in the RES + OCM, whereas crypt abundance was less (p = 0.03) in +OCM compared to −OCM. An interaction was observed for SLC5A1 (p ≤ 0.02), with the least villus and total abundance in CON – OCM, whereas crypt abundance was reduced in RES + OCM. These findings highlight the adaptive nature of the fetal small intestine to maternal dietary stress and indicate that OCM supplementation may help optimize fetal glucose metabolism and nutrient absorption.