352. Maternal Undernutrition Alters Muscle Fiber Type Composition and Metabolomic Profile in the Psoas Major Muscle of Japanese Black (Wagyu) Cattle Fetuses.

Abstract

Early-life nutrition affects skeletal muscle characteristics in cattle. This nutritional modulation affects muscle metabolism and fiber type composition, potentially influencing muscle productivity and meat quality in later life. In this study, we focused on the psoas major muscle, which is important for meat production as a fillet cut, and aimed to elucidate the effects of differences in maternal nutritional conditions on the fetal psoas major muscle through analyses of myofiber type composition and metabolomic profiling. Multiparous Wagyu cattle were randomly assigned to either a control group (CON; 120% of Japanese feeding standard for beef cattle, n = 5) or a maternal undernutrition group (MUN; 60% of Japanese feeding standard for beef cattle, n = 6) from conception to day 260 of gestation. Fetuses were harvested at approximately day 260 of gestation and fetal psoas major muscle samples were collected. Immunofluorescent staining was performed to evaluate myofiber characteristics. Metabolites of the psoas major muscle were analyzed using CE-TOFMS and LC-TOFMS. Differential metabolites were identified using Welch’s t-test (p < 0.1), followed by pathway enrichment analysis. Fetal body weight and the psoas major muscle weight were lower (p < 0.05) in the MUN group than in the CON group. The proportion of type 1 myofibers was lower (p < 0.01) in the MUN group, whereas the proportions of type 2A and type 2X myofibers did not differ between groups (p > 0.43). Metabolomic profiling detected 477 metabolites in the fetal psoas major muscle, of which 16 differed between groups at p < 0.05. Among these, the MUN group showed lower levels of metabolites including UDP-galactose, myo-inositol 3-phosphate/myo-inositol 1-phosphate, and succinic acid, whereas acylcarnitine (18:2)-1 and phenylalanine were higher than in the CON group. Pathway analysis identified amino sugar and nucleotide sugar metabolism as the most significantly enriched pathway. These findings suggest that maternal undernutrition alters both muscle fiber-type characteristics and metabolic profiles in the fetal psoas major muscle of Wagyu cattle. In particular, the reduction in type 1 fibers, together with changes in metabolites related to energy and nucleotide sugar metabolism, indicates that maternal undernutrition may impair the establishment of oxidative muscle properties and alter myogenesis and muscle development during the fetal stage.