The rumen microbiome and its metabolome together with the host metabolome regulate the growth performance of crossbred beef cattle

In this study, healthy Simmental with similar birth date and weight were selected as dams, Simmental (Combination I), Belgian Blue (Combination II) and Red Angus (Combination III) were used as parents for crossbreeding. The progeny of the three combination crosses were measured for growth performance under identical conditions from birth rearing to 18 months of age (n=30). Rumen fluid and plasma were collected for macro-genomic and non-targeted metabolomic analysis (n=8). The results showed that Combination II was superior to Combination I and Combination III in body weight (BW), body height (BH), cross section height (CSB) and body slant length (BSL) (P < 0.05). Mycoplasma, Succinivibrio, Anaerostipes, Methanosphaera, Aspergillus, and Acidomyces were significantly increased in the rumen of Combination II (P < 0.05), whereas differentially expressed metabolites (DEMs) 9,10,13-Trihome (11), 9,12,13-Trihome and 9(10)-Epome, and 9(S)-Hpode were reduced in abundance. In addition, plasma DEM PC (14:0/P-18:1(11Z)), PC (16:0/0:0), and PC (17:0/0:0) were down-regulated in combination II. Correlation analysis showed that Anaerostipes, Methanosphaera and Succinivibrio were associated with PC (14:0/P-18:1(11Z)), 9(10)-Epome, 9,10,13-Trihome (11), 9(S)-Hpode, 9,10,13-Trihome, PC (17:0/0:0) and PC (16:0/0:0) were significantly negatively correlated and significantly positively correlated with growth traits (P < 0.05).