This study aimed to investigate the effects of fumarate and nitroglycerin on rumen fermentation, methane and hydrogen production, and microbiota. In vitro rumen fermentation was used in this study with four treatment groups: control (CON), fumarate (FA), nitroglycerin (NG) and fumarate plus nitroglycerin (FN). Real-time PCR and 16S rRNA gene sequencing were used to analyze microbiota. The results showed that nitroglycerin completely inhibited methane production and that this resulted in hydrogen accumulation. Fumarate decreased the hydrogen accumulation and improved the rumen fermentation parameters. Fumarate increased the concentration of propionate and microbial crude protein, and decreased the ratio of acetate to propionate in FN. Fumarate, nitroglycerin and their combination did not affect the abundance of bacteria, protozoa and anaerobic fungi, but altered archaea. The PCoA showed that the bacterial (Anosim, R = 0.747, p = 0.001) and archaeal communities (Anosim, R = 0.410, p = 0.005) were different among the four treatments. Compared with CON, fumarate restored Bacteroidetes, Firmicutes, Spirochaetae, Actinobacteria, Unclassified Ruminococcaceae, Streptococcus, Treponema and Bifidobacterium in relative abundance in FN, but did not affect Succinivibrio, Ruminobacter and archaeal taxa. The results indicated that fumarate alleviated the depressed rumen fermentation caused by the inhibition of methanogenesis by nitroglycerin. This may potentially provide an alternative way to use these chemicals to mitigate methane emission in ruminants.

The aim of the present study was to explore the effects of dietary non-fibrous carbohydrate to neutral detergent fiber (NFC/NDF) ratios on rumen development of calves, and to investigate the mechanisms by integrating of lncRNA and mRNA profiling. Forty-five weaned Charolais hybrid calves [body weight = 94.38 ± 2.50 kg; age = 70 ± 2.69 d] were randomly assigned to 1 of 3 treatment groups with different dietary NFC/NDF ratios: 1.10 (H group), 0.94 (M group) and 0.60 (L group), respectively. The ventral sac of the rumen was sampled for morphological observation and transcriptional sequencing. The average daily gain of calves in the high NFC/NDF ratio group was significantly higher than that in other groups (p < 0.05). Papillae width was largest in high NFC/NDF ratio group calves (p < 0.05). Identified differentially expressed genes that were significantly enriched in pathways closely related to rumen epithelial development included focal adhesion, Wingless-int signaling pathway, thyroid hormone signaling pathway, regulation of actin cytoskeleton and cGMP-PKG signaling pathway. The lncRNA-mRNA network included XLOC_068691 and MOAB, XLOC_023657 and DKK2, XLOC_064331 and PPP1R12A which we interpret to mean they have important regulatory roles in calve rumen development. These findings will serve as a theoretical basis for further analysis of the molecular genetic mechanism of dietary factors affecting rumen development in calves.

The gastrointestinal tract of ruminants hosts a specialized microbial ecosystem that has evolved to efficiently digest fiber. However, modern intensive farming practices, which often involve reduced dietary fiber and increased grain supplementation, are linked to metabolic disorders in ruminants. Despite this, the understanding of the taxonomic and functional adaptations of the gastrointestinal microbiome to dietary changes remains limited, largely due to the challenges in obtaining high-resolution characterization of microbial communities. This study employed genome-resolved metagenomics to examine how a starch-rich (SR) grain-based diet compares to a fiber-rich (FR) hay-based diet in shaping the composition and function of the gastrointestinal microbiome in the rumen, jejunum, and cecum of Hu sheep. A total of 10 sheep (approximately 180 d old, with a body weight of 25.6 ± 0.41 kg) were allocated to the 2 dietary groups (SR and FR groups) for a 28-d experimental period, and metagenomic sequencing was performed on digesta samples from different gastrointestinal regions. Using a representative microbial gene catalog (RGMGC) and 10,373 metagenome-assembled genomes from previous studies,microbial composition, strain-level diversity, and carbohydrate-active enzyme profiles at higher taxonomic and functional resolution were analyzed. The results showed that the transition from the FR diet to the SR diet significantly altered the fermentation patterns and the structure and function of the sheep gastrointestinal microbiota. Community analysis revealed microbial taxa such as Prevotella spp., Alistipes spp., RC9 spp., CAG-110 spp., and Akkermansia spp. with significantly altered abundances (P < 0.05), primarily associated with the reduced fiber content in the SR diet. Moreover, the gastrointestinal microbiome exhibited strain-level changes in carbohydrate degradation, leading to reduced metabolic functions necessary for fiber processing. Comparative genomics at the single-genome level pinpointed Prevotella as a core genus with strains showing significant functional differences, notably in the capacity to degrade plant polysaccharides. Overall, these findings provide new insights into microbial regulation of gastrointestinal health and offer valuable enzyme gene resources in ruminants.