Abstract
Dairy cattle with high (HM) versus low muscle (LM) reserves exhibit distinct temporal changes in longissimus dorsi muscle depth (LDD) in late gestation. Branched-chain volatile fatty acids (BCVFA) supplementation increased blood glucose levels. We hypothesized that differences in HM and LM reflect distinct muscle metabolism and BCVFA supplementation altered metabolic pathways. At 42 d before expected calving (BEC) Holstein dairy cows were enrolled in a 2 x 2 factorial study of diet and muscle reserves, by assigning to control (CON) or BCVFA supplemented diets and LDD of HM (>4.6 cm) or LM (≤4.6 cm) groups: HM-CON (n=13), HM-BCVFA (n=10), LM-CON (n=9), and LM-BCVFA (n=9). Longisumus dorsi was biopsied at 21 d BEC, total RNA isolated and protein coding gene expression measured with RNA-seq. Between HM and LM 713 genes were differentially expressed and 481 between BCVFA and CON (P<0.05). Transcriptional signatures indicated differential distribution of Type II fibers between groups, with MYH1 greater in LM and MYH2 greater in HM cattle (P<0.05). Signatures of LM cattle relative to HM indicated greater activation of autophagy, ubiquitin-proteasome, and Ca2+-calpain pathways. HM cattle displayed greater expression of genes that encode extracellular matrix proteins and factors that regulate their proteolysis and turnover. BCVFA modified transcriptomes by increasing expression of genes that regulate fatty acid degradation and flux of carbons into the TCA cycle as acetyl CoA. Molecular signatures support distinct metabolic strategies between LM and HM cattle, and that BCVFA supplementation increased substrates for energy generation.
Published Version
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