Effects of plane of nutrition during late gestation and weaning age on transcriptome profiles of Longissimus muscle in Simmental x Angus offspring
The aim of this study was to evaluate potential carryover effects of maternal diet during late gestation and effects of weaning age on the transcriptome profiles of Longissimus muscle of Angus x Simmental offspring. Pregnant cows blocked by breed were utilized in a 2 x 2 factorial design. Three months prior to the projected parturition date, cows were assigned to diets (low or medium plane of nutrition). Low plane of nutrition was achieved by grazing endophyte-infected tall fescue/red clover pastures with no supplement, while medium plane of nutrition was achieved by grazing endophyte-infected tall fescue/red clover pastures supplemented with 2.3 kg of dried distiller’s grains with solubles and soyhulls. Steer calves were randomly assigned to early or normal weaning treatments within each gestational diet (n=20). At 80 d postpartum, early-wean offspring (EW) were weaned, and received a high-energy finishing diet. At 186 postpartum, normal-wean offspring (NW) were weaned and joined EW steers at the feedlot where they received the same diet. Longissimus muscle (LM) biopsies were harvested on 81, 187 and 354 days of age. A 45,220 bovine microarray (Agilent) was used for transcript profiling (n=5 steers/group). Functional analysis was performed by means of the Dynamic Impact Approach (DIA). ANOVA statistical analysis (FDR<0.05 and P<0.05) revealed 8,400 differentially expressed genes (DEG) due to time alone and 856 DEG due to treatment alone. Treatment × time affected 33 genes and no DEG were detected for time × treatment × diet. Within the 8,400 DEG, the functional analysis revealed that nitrogen metabolism and drug metabolism were the canonical pathways with the highest impact, specially comparing 81 to 354 days of age (P < 0.05). For the 856 DEG due to treatment, fatty acid biosynthesis, pyruvate metabolism and insulin signaling pathways were the most–impacted when comparing EW to NW at different time points. Within the 33 DEG due to treatment × time fatty acid biosynthesis was the only impacted canonical pathway (P < 0.05). Moreover, initial analysis based on expression pattern (i.e., up- or down-regulation) of the 33 DEG indicated most were activated. Results indicated a minor response of the offspring transcriptome to level of maternal plane of nutrition at least when applied during the last 90 days of pregnancy. Post-natal nutritional management, however, led to marked differences in transcriptomics particularly between the growing (81 to 187 days) and finishing phases (187 to 354 days).
Keywords: nutrigenomics, bioinformatics, nutrition