Unveiling the Role of Rumen Microbiome in Modulating Intramuscular Fat Deposition of Pingliang Red Cattle

Pingliang Red cattle is renowned for its tender meat and symmetrical intramuscular fat (IMF) deposition. Rumen microbiota are crucial for energy metabolism and nutrient acquisition in cattle, significantly influencing IMF deposition. Therefore, this study aimed to explore how rumen microbiota impact IMF deposition in Pingliang Red cattle. 34 castrated Pingliang Red cattle were subjected to the same management for 2 months, followed by centralized and unified slaughtering. Based on the measured IMF content in the longissimus dorsi, 18 cattle were selected and divided into a high-intramuscular-fat group (HIMF, n = 9) and a low-intramuscular-fat group (LIMF, n = 9). Rumen fluid was subsequently collected for metagenomic sequencing. Results showed significant differences in taxonomic abundance at both the genus and species levels, the relative abundance of carbohydrate-active enzyme (CAZy) families, and functional profiles (p < 0.05). Specific rumen microbes, such as Limosilactobacillus panis (AUC = 0.765) and Fibrobacter succinogenes (AUC = 0.753), served as potential biomarkers for HIMF deposition in Pingliang Red cattle. With the exception of Bacillus, Fibrobacter succinogenes, Limosilactobacillus panis, Prevotella intermedia, and Streptomyces exhibited positive correlations with IMF content. Functional analysis based on KEGG orthology (KO) indicated that specific enzymes promote IMF deposition by regulating the metabolism of short-chain fatty acids (SCFAs), long-chain fatty acids (LCFAs), and lipopolysaccharides, as well as insulin signaling. These findings provide a theoretical reference for regulating rumen microbial communities to improve IMF deposition.