426 Effects of maternal nutritional restriction on beef cattle fetal metabolism

Abstract Cellular respiration is the metabolic process that breaks down glucose by use of oxygen to produce ATP. It consists of three main steps: glycolysis, the TCA cycle and oxidative phosphorylation. Oxidative phosphorylation provides most of the ATP for body functions. If oxidative phosphorylation is downregulated, then cellular metabolism will be disrupted. The objective of this study was to identify the cellular pathways impacted by maternal nutrient restriction in beef cattle. A total of 36 fetuses were examined: 18 fetuses from dams that were given either a restricted (RES) or an adequate (ADQ) diet from d 160 to 240 of gestation. At d 240 of gestation, dams underwent Cesarean section for fetal removal, morphometrics, blood and tissue collection. Liver tissue samples were sequenced via Illumina platforms and analyzed by DESeq2, while the screening threshold was set at |log2(FoldChange)| >= 1 and padj <= 0.05. Enrichment analysis of the differential expressed genes (DEGs) was performed by annotating genes to biological processes (Gene Ontology terms) and metabolic pathways (KEGG pathways). Genes with an adjusted P-value ≤ 0.05 were assigned as differentially expressed. Morphometrics data was evaluated by mixed procedures of SAS and significant was declared at P < 0.10. There was a significant group effect of the fetal necropsy weights (25.5 ± 0.55 vs 23.0 ± 0.60, kg, for ADQ and RES respectively, P < 0.02). Further, there was a significant group effect on the fetal liver weights (485.20 ± 29.19 vs 394.90 ± 29.19 g, for ADQ and RES, respectively, P < 0.07). RES fetuses exhibited 704 uniquely expressed genes compared with ADQ fetuses that showed 304 uniquely expressed genes. However, 13,145 genes were co-expressed by RES and ADQ Fetuses. A total of 2,327 genes were identified as differentially regulated between the groups. Of these 1,106 genes were up-regulated and 1,221 are down-regulated in RES vs. ADQ fetuses. KEGG pathway enrichment analysis showed downregulation of key enzymes involved in oxidative phosphorylation specifically in complexes I, II, III and IV. Thus, downregulation of oxidative phosphorylation is a potential mechanism by which maternal restriction retards fetal growth and development as seen in this project. Funded by NIFA CBG # 2021-38821-34599.