The Influence Of Breed, Growing Phase Nutrition, And Finishing System (Pasture Vs. Feedlot) On The Relative Abundance Of Mrna Associated With Lipid Metabolism In Longissimus Muscle

Abstract The objective of this experiment was to evaluate the influence of beef cattle breed, nutritional treatment, and finishing strategy (pasture vs. feedlot) on the relative abundance of mRNA associated with lipid metabolism in longissimus muscle (LM). Eighty-three uncastrated males from three genetic groups: Nellore (N), ½ Angus x ½ Nellore (A) and ½ Senepol x ½ Nellore (S), were randomly assigned to dietary treatments supplied during the growing phase. Treatments consisted of mineral supplement or concentrate supplement (0.3% BW). Following the growing phase, two replicates within each treatment x breed group were randomly assigned to one of two finishing systems (Figure 1): Pasture grazing + concentrate (PC) and Conventional feedlot (CF), both are supplemented at 2% BW/had/d (Table 1). After 209 days the animals were slaughtered, an LM sample (5.0g) was removed between 12th and 13th ribs from each animal and frozen (liquid nitrogen). The relative abundance of mRNA associated with lipid metabolism was measured by qRT-PCR. Target genes include PPARα, PPARγ, SREBP1c, SCD1, LPL, FBP4, CPT2, ACOX and ACCα. The ∆∆ Ct was used to calculate the data and analyzed using the mixed procedures of SAS for a 3×2×2 factorial arrangement of treatments. Mineral supplementation during the growing phase increased (P < 0.05) the relative abundance of mRNA of PPARα and PPARγ compared to concentrate. The relative abundance of PPARγ, SREBP1c, SCD1, FABP4, ACOX, was greater (P < 0.05) in CF compared to PC. Angus LM muscle showed greater (P < 0.05) relative abundance of SREPB1c compared to Nellore and Senepol. The muscle of Nellore and Angus had greater (P < 0.05) relative abundance of PPARα SCD1 and lower (P < 0.05) of PPARγ when compared to Senepol breed. Therefore, in this study, the conventional feedlot and Angus are more positively associated with differential expression of adipogenic genes.