This study examined the impact of resveratrol (RES) on growth performance, meat quality, and intramuscular fat (IMF) deposition in steers undergoing finishing. Thirty healthy Angus steers with similar body weights (mean 571.83 ± 5.27 kg) were divided into three groups (n = 10) and fed the following diets for 240 d: 1) basal diet, 2) basal diet containing 400 mg/kg RES, or 3) basal diet containing 800 mg/kg RES. The results showed that supplementation with 400 mg/kg RES significantly increased the final body weight and average daily gain of steers (P < 0.05), whereas the 800 mg/kg group did not show a significant effect. Moreover, 400 mg/kg RES significantly increased the live weight before slaughter and carcass weight while reducing subcutaneous backfat thickness (P < 0.05). Additionally, both levels of RES supplementation significantly increased the IMF content in the Longissimus lumborum (LL) muscle and reduced drip loss, cooking loss, and shear force (P < 0.05). Notably, 400 mg/kg RES supplementation significantly decreased adipose triglyceride lipase and hormone-sensitive lipase activities of LL muscle and acetyl-CoA carboxylase activity was enhanced in all RES-treated groups (P < 0.05). These results integrating transcriptomics, proteomics, real-time quantitative PCR, and Western blotting revealed that RES upregulated both the mRNA and protein expression levels of fatty acid transport-related factors (fatty acid transport protein 1, fatty acid-binding protein 3, and fatty acid-binding protein 4) and lipogenesis-related factors (acetyl-CoA carboxylase and diacylglycerol O-acyltransferase 1) in the PPAR signaling pathway of the LL muscle. Collectively, dietary 400 mg/kg RES improved growth performance and carcass traits, specifically enhancing meat quality and promoting IMF deposition of the LL muscle. These effects were primarily mediated through activating the peroxisome proliferator-activated receptor signaling pathway, which enhances the expression of factors related to fatty acid uptake and transport, lipid synthesis.

In this study, we aimed to characterize intramuscular fat (IMF) tissue in fattening steers through a comparison with subcutaneous fat (SCF) tissue. The IMF of the longissimus thoracis et lumborum and the SCF of the back fat from three fattening steers (mean body weight of 703.50 ± 11.45 kg) were collected, and the muscle tissue, connective tissue, and fascia were carefully removed. Gene and protein expressions and the lipid contents were assessed via transcriptomic, proteomic, and lipidomic analyses, respectively. Subsequently, tissue-specific factors were identified using integrated analysis. The results revealed that the expressions of sarcoplasmic/endoplasmic reticulum Ca²⁺ transporting 2 (ATP2A2), enolase 3 (ENO3), fructose-bisphosphatase 2 (FBP2), myosin heavy chain 7 (MYH7), myosin light chain 3 (MYL3), myosin light chain kinase (MYLK), glycogen phosphorylase (PYGM), troponin C1 (TNNC1), and tropomyosin 2 (TPM2) significantly increased in IMF at both the mRNA and protein levels, whereas those of fatty acid-binding protein 4 (FABP4), stearoyl-CoA desaturase (SCD), and apolipoprotein E (APOE) were reduced. The abundances of both phosphatidylinositol (PI) (18:1/20:4) and phosphatidylcholine (PC) (15:0/18:2) were positively correlated with APOE. Conversely, that of PI (18:1/20:4) was negatively correlated with ENO3 and PYGM, whereas PC (15:0/18:2) was negatively correlated with TNNC1 and MYLK. In conclusion, we identified calcium signaling and glycolysis as key IMF-regulating pathways. ATP2A2, ENO3, FBP2, MYH7, MYL3, MYLK, PYGM, TNNC1, TPM2, and LPE 18:0 were negatively associated with IMF deposition, whereas FABP4, SCD, APOE, PI (18:1/20:4), and PC (15:0/18:2) were positively associated with it. These findings offer underlying IMF-related targets to promote IMF deposition in cattle.