Introduction This study evaluated the effects of different dietary inclusion levels of high-moisture corn (HMC) on the growth performance and rumen metabolism of young Simmental bulls. Methods Thirty-two young Simmental bulls (243.99 ± 13.52 kg) were randomly allocated to one of four dietary treatments: (1) control group (HMC0), fed a basal diet; (2) HMC15 group, where 15% of the conventional corn in the diet was replaced with HMC; (3) HMC30 group, with a 30% replacement level of HMC; and (4) HMC45 group, with a 45% replacement level of HMC. Live body weights were recorded from all bulls on days 0, 30, 60, and 120. On day 120, rumen fluid samples were also obtained, filtered, and properly preserved at −80 °C for later determination of rumen fermentation and nutrient metabolism profiles. Results The results demonstrated that on day 120, the body weights of the HMC30 and HMC45 groups were significantly higher than that of the HMC0 group ( p 0.05). Dietary HMC supplementation significantly improved the average daily gain (ADG) and profit of young Simmental bulls ( p 0.05). In contrast, the HMC45 group showed significantly lower acetic acid and total volatile fatty acids (total VFA) concentrations compared to the HMC0 group, while the lactic acid (LA) concentration was the opposite( p 0.05). Furthermore, a trend of decreasing ruminal pH was observed with increasing HMC inclusion levels. Concurrently, HMC feeding significantly enhanced the alpha diversity of the rumen microbiota. Rumen metabolomics revealed distinct metabolic alterations in the HMC45 group, identifying 52 differential metabolites—including 1,2-Dioleoyl-sn-Glycero-3-Phosphocholine (DOPC), PC, taurine, and L-glutamic acid—which were primarily involved in key pathways such as glycerophospholipid metabolism, bile acid metabolism, and glutamate metabolism. Discussion In conclusion, the 45% HMC substitution level significantly enhanced the production performance of young Simmental bulls by modulating key metabolites involved in glycerophospholipid metabolism, bile secretion, and amino acid metabolism, thereby enriching rumen microbial diversity and ultimately improving growth outcomes
Gao et al. (Wed,) studied this question.