PSXI-29 Rumen microbiome and in vitro digestibility of goats divergent in feed efficiency.

Abstract The composition and function of the rumen microbiome are critical for ruminant feed efficiency. To investigate this in Chinese local goats (Jianzhou Daer Capra hircus), we compared in vitro fermentation characteristics and microbiome of rumen contents of goats divergent for feed efficiency. Two cohorts with divergent residue feed intake (high and low feed efficiency; n = 12) were selected from 84 Jianzhou Daer goats (initial body weight = 29.1 ± 0.32 kg) during a 90-d feeding trial. Goats were offered ad libitum access to a total mixed ration that consisted of 28% corn, 22% corn silage, 20% peanut seedlings, 13.2% soybean meal, 10% alfalfa granules, 3.8% wheat bran, and 3% premix supplement (dry matter basis). At the end of the trial, rumen liquid and digesta (solid + liquid) from six randomly selected goats per group were collected for in vitro fermentation and metagenomic sequencing. The high feed efficiency cohort gained more weight and exhibited a lower feed conversion ratio (both P < 0.001). Rumen liquid from the high efficiency group produced more gas (P = 0.039), acetate (P = 0.036), and butyrate (P = 0.012), and resulted in a higher total volatile fatty acid level after a 24 h of fermentation (P = 0.035). Metagenomic analysis revealed that the Chao index of microbial species was greater in the high efficiency group (P = 0.043). The relative abundance levels of Bifidobacterium, Pseudoscardovia, and Scardovia were enriched in rumen contents of the high efficiency group, whereas those of Treponema, Roseburia, Barnesiella, Muribaculum were higher in the low efficiency group. KEGG function prediction showed enriched microbiota in high efficiency goats were associated with biosynthesis pathways (amino acids, secondary metabolites, and nucleotide sugars, streptomycin, acarbose and validamycin), while microbiota dominated in the low efficiency group were associated with flagellar assembly, pyruvate metabolism, and biofilm formation. Alignment of differential taxa-genome data to the carbohydrate-active enzyme (CAZy) database revealed that the high efficiency goats’ microbiota contained more genes related to glycosyl transferases (GT2, GT39, GT98), whereas the low efficiency group’s microbiota contained more genes related to glycosyl hydrolases (GH10, GH149, GH146). These findings indicate that the rumen microbiome of high-efficiency goats undergoes compositional and functional shifts toward nutrient synthesis pathways and demonstrated enhanced feed digestibility.