This study investigated the technological properties and volatile flavor profiles of tallow from three anatomical regions of Wagyu cattle, omental fats (OF), perirenal fats (PF), and subcutaneous fats (SF), smelted at temperatures ranging from 100 to 160 °C. The objective was to provide a theoretical basis for the targeted utilization of Wagyu fats. Results showed that smelting temperature significantly affected oil yield, with the highest yield obtained at 160 °C for all regions. PF exhibited the greatest oil yield, followed by OF and SF. Physicochemical analyses indicated that OF had the highest degree of unsaturation, whereas PF demonstrated superior hardness and oxidative stability. Microstructural and spectroscopic analyses, Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) were employed to characterize the samples, revealed that the compact protein structure of SF residues limited oil release, while the porous structures of OF and PF residues facilitated higher yields. With respect to flavor profiling, headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry (HS-SPME-GC-MS) was employed to analyze volatile compounds, identified aldehydes as the dominant flavor contributors in OF and PF, imparting fatty and citrus notes, whereas SF was characterized by a distinct creamy aroma primarily due to γ-butyrolactone. These regional differences were further validated by principal component analysis (PCA). Overall, PF obtained the highest comprehensive quality score. The integrated evaluation underscores the potential for precision-based utilization of Wagyu tallow: PF and OF are recommended for applications demanding high yield and intense flavor, whereas SF, characterized by its distinctive creamy aroma, is more suitable for specialized or niche products.

High-concentrate feeding during late fattening can impair metabolic health and meat quality in beef cattle, yet effective nutritional strategies remain limited. Choline and nicotinic acid are involved in lipid and energy metabolism, but information on their combined or sequential supplementation is scarce. This study evaluated rumen-protected choline given alone or together with nicotinic acid on growth performance, meat quality, serum biochemical indices, serum metabolomics, and free amino acid profiles in late-fattening beef cattle. Twenty-four black cattle were randomly allocated to three groups: CON (basal diet), CC (basal diet + 10 g/d RPC for 90 d), and CC-CNA (basal diet + 10 g/d RPC for 90 d + 10 g/d protected NA during the final 30 d). Shear force was significantly lower in both CC and CC-CNA than in CON (p < 0.05), indicating improved tenderness. Exploratory serum metabolomics identified treatment-associated metabolites and pathways related to amino acid, purine, sphingolipid, and lipid metabolism. Taste-related free amino acids were also altered by supplementation (p < 0.05). RPC alone or with short-term NA may improve tenderness and modulate systemic metabolic responses; larger studies with direct sensory evaluation are needed to confirm growth and flavor-related effects.