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The ability to improve meat quality and production efficiency in cattle is limited by an inability to enhance marbling and simultaneously limit undesirable adipose tissue accretion. The objective of this study was to examine expression of regulatory genes in subcutaneous (SCF) adipose tissue of heifers in response to increasing days on feed (DOF) and finishing strategy. Crossbred heifers (n = 24) were allotted as follows: Group 1 = 0 d, Group 2 = 99 d on winter annual ryegrass (grass; Lolium multiflorum Lam.), Group 3 = 218 g on grass, Group 4 = 99 d on grass followed by 119 d on grain. Adipose tissue samples were collected at time of harvest and frozen. Carcass characteristics were measured 24 h postharvest. As expected, HCW (P0.0001), ribeye area (REA; P0.0002), backfat (BF; P0.0001), KPH (P0.0001), and marbling score (P0.0009) increased with DOF though frame score was not different (P0.95). Average daily gain decreased with DOF (P0.0001). Yield grade increased (P0.0014) but cook loss percentage decreased (P0.001) with DOF without changes in 24-h pH (P0.31). Interestingly, Warner-Bratzler shear force (WBS) was decreased with DOF (P0.0089). Meanwhile, BF (P0.01) and KPH (P0.05) were greater, whereas marbling values trended greater in grain versus grass-finished heifers. Neither ADG (P0.89), HCW (P0.26), frame score (P0.85), nor REA (P0.38) were different between these groups. Grain finishing increased yield grade (P0.001) but did not affect 24-h pH (P0.88), cook loss percentage (P0.98), or WBS (P0.44) compared with grass-finished heifers. The expression of PPARγ, bone morphogenic protein 2 (BMP2), and SMAD family member 1 (SMAD1) mRNA was upregulated in response to DOF and grain finishing, whereas sterol regulatory element binding protein 1c (SREBP-1c), sonic hedgehog (SHH), chicken ovalbumin protein transcription factor 1 (COUP-TF1), chicken ovalbumin protein transcription factor 2 (COUP-TF2), and preadipocyte factor-1 (PREF-1) mRNA was decreased in response to DOF and grain finishing. These changes were associated with increased expression of lipoprotein lipase (LPL), stearoyl-coenzyme A desaturase (SCD), and fatty acid synthase (FAS) mRNA. In summary, increasing DOF was associated with improved meat quality whereas gene expression studies suggest several novel genes are associated with subcutaneous adipose tissue development in growing and finishing cattle. |
