349. Award Talk: Effects of Betaine Supplementation and Nutrient Restriction During Gestation Onfetal Muscle Development and Oxidative Status in Sheep.

Abstract Maternal nutritional status during gestation impacts fetal myogenesis and liver oxidative balance, thereby altering growth and metabolic function. Supplementation of betaine, a methyl donor, supports muscle development and antioxidant capacity, and improves physiological responses. We hypothesized that maternal nutrient restriction during gestation would impair fetal muscle development and alter fetal liver antioxidant status, while betaine supplementation would alleviate the negative effects of maternal nutrient restriction. To test this hypothesis, 32 multiparous Dorset ewes were estrus-synchronized and bred to one of three related rams. Ewes pregnant with twins were assigned to one of four diets [100% NRC requirements (CON), 60% NRC (RES), CON+betaine (CON+BET; 2 g/day), and RES+BET] from day 30 to 130 of gestation. The offspring included 27 males (CON:8, RES:5, CON+BET:5, RES+BET:9) and 37 females (CON:8, RES:9, CON+BET:11, RES+BET:9). Maternal blood was collected on days 30 and 130 of gestation, and at necropsy on day 130, fetal semitendinosus (STN) and longissimus dorsi (LM) muscles, and liver were collected for immunohistochemistry and oxidative status, respectively. Malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GPx) were measured in maternal plasma and fetal liver isolates using commercially available assay kits. Data were analyzed using RStudio with ANOVA, including fetal sex as a covariate, with P ≤ 0.05 considered significant and 0.05 < P ≤ 0.10 as a tendency. In fetal STN, the percentage of Pax7-positive cells was reduced in RES compared with CON and RES+BET (P ≤ 0.01). In contrast, the percentage of Pax7-positive cells in the LM was not affected by maternal diet (P = 0.65). Male fetuses from RES ewes had greater type I and fewer type II fibers compared with RES+BET males in STN (P = 0.03). Maternal plasma MDA concentration, SOD, and GPx activities did not differ among diet groups at day 30 of gestation (P ≥ 0.20). At day 130, maternal plasma GPx activity tended to be reduced in RES+BET (5.86±1.12 U/mL) compared with CON+BET (10.26±1.28 U/mL; P = 0.08), while MDA and SOD were not different (P ≥ 0.64). Fetal liver SOD and GPx activities were greater in CON (40±1.95 and 74.5±3.55 U/mg protein, respectively) and CON+BET (35.7±2.18 and 77±4.13 U/mg protein) than in RES (27±2.64 and 58±4.16 U/mg protein) and RES+BET (29±1.90 and 63±3.70 U/mg protein; P ≤ 0.001). Fetal liver MDA concentrations were not affected by maternal diet but tended to be greater in males (0.133±0.007 nmol/mg protein) than females (0.114±0.006 nmol/mg protein; P = 0.06). Overall, maternal nutrient restriction altered fetal muscle development and liver antioxidant capacity, with betaine supplementation providing partial, tissue specific responses, highlighting the need for further study of betaine as a targeted nutritional intervention during maternal nutrient restriction.