Intensive nursing and feeding during the early growth period altered intramuscular adipogenesis in crossbred steers (Japanese Black male x Holstein female)

We investigated the influence of feed quality during the early growth stage on expression of adipogenic genes in skeletal muscle of crossbred cattle. The cattle were divided three groups at 45 days of age group high energy (H: n = 7), group normal energy (N: n = 7) and group roughage (R: n = 7). Cattle in group H were three fold-intensively fed a high protein and low fat milk replacer (Crude Protein (CP): 28%, Ether Extracts (EE): 18%, max: 2.0 kg, 12 L day^-1) from 45 days to 4 months of age. In groups N and R, cattle were fed a normal milk replacer (CP: 25%, EE: 23%, max: 0.5 kg, 4 L day^-1) from 45 days to 4 months of age. From 4-10 months of age, cattle in group H were fed a high-nutrition Total Mixture Rate (TMR), while group N were fed a normal-nutrition TMR and group R were fed only roughage. Muscle samples were taken by biopsy from Longissimus thoracis muscle (LT) at 45 days, 4 and 10 months of age. Results from assays using quantitative real-time Polym erase Chain Reaction (PCR) revealed that gene expression of Peroxisome Proliferator-activated Receptor Gamma 2 (PPARγ2), CCAAT/Enhancer-Binding Protein alpha (C/EBPα), Stearoyl-CoA Desaturase (SCD), Glucose-6-Phosphate Dehydrogenase (G6PD), Fatty Acid Synthase (FASN) and Leptin related to adipogenesis and fatty acid synthesis differed among groups. The expression of these genes was significantly different among groups at 10 months but not at 4 months of age. These results demonstrated that differences in feed quality during early growth stages had substantial effects on the expression of genes related to adipogenesis and fatty acid synthesis in LT.