Slaughter performance is a critical economic trait that varies across breeds, yet the rumen metabolic mechanisms driving these phenotypic differences remain unclear. The study involved 30 healthy 12-month-old beef cattle, with 10 animals from each of the three breeds: Chinese Simmental (ST), Taihang Yun (TY), and Charolais (CL). The cattle were randomly assigned into three groups using a completely randomized design, and the average initial body weight was 549.78 ± 59.45 kg. A 130-day feeding trial (10-day pre-feeding period, 120-day main trial period) was conducted. By comparing the slaughter performance, relative organ weight, and rumen fluid metabolomic profiles, the study investigated breed-specific differences in meat quality and potential underlying metabolic patterns. The results showed that CL exhibited a superior carcass yield, with a significantly higher dressing percentage (62.38%, p = 0.013) and net meat percentage (56.54%, p = 0.028) than ST and TY, and a significantly lower backfat thickness (p = 0.006); ST had the highest proportion of premium cuts, relative to carcass weight (72.97%, p = 0.014), with prominent economic value, while TY had significantly higher weights of visceral organs, such as liver, kidney, small intestine and omasum, than CL (p < 0.05). Metabolomic analysis revealed that CL and ST had elevated levels of purine metabolism, nucleotide synthesis and cofactor biosynthesis compared to TY. In conclusion, CL and ST possess advantages in carcass yield supported by upregulated anabolic metabolism in the rumen, whereas TY prioritizes visceral organ development. These findings provide valuable insights into the physiological and metabolic divergences regulating the slaughter performance and regional adaptability across cattle breeds.