理学最新文献

Background: Yeast enzyme hydrolysis slurry (YS) has the potential to optimize feed utilization efficiency and improve the health of farmed animals, as it contains abundant bioactive components like small-molecule peptides and amino acids. However, its function and application effects in juvenile largemouth bass (Micropterus salmoides) are unclear.

Methods: Three hundred and twenty largemouth bass (8.20 ± 0.05 g) were randomly divided into four groups (4 replicates of 20 fish). Four isonitrogenous (52%) and isolipidic (10%) diets were formulated: FM group (positive control), SBM group (soybean meal replaced 30% of fish meal protein, negative control), and the SBM group supplemented with 1% YS (SBM + 1% YS) and 2% YS (SBM + 2% YS), respectively. After a 56-day feeding period, the fish were assessed for growth, intestinal health, and metabolic regulation-related indices.

Results: Our study found that weight gain rate (P = 0.032) and specific growth rate (P = 0.030) in the SBM + 1% YS and SBM + 2% YS groups were significantly higher than those in the SBM group. Relative to the SBM group, YS-supplemented groups exhibited marked elevations in intestinal folds, goblet cell numbers, serum acid and alkaline phosphatase activities, catalase and superoxide dismutase activities, as well as the activities of key digestive enzymes (lipase, α-amylase, pepsin, chymotrypsin), accompanied by downregulated mRNA expression of anorexigenic genes cholecystokinin and leptin. Meanwhile, these groups showed significantly lower serum D-lactate, diamine oxidase, lipopolysaccharide levels and malondialdehyde content. The abundance of beneficial genus Cetobacterium increased while the abundance of pathogenic genus Edwardsiella (P = 0.0265) significantly reduced in SBM + 1% YS and SBM comparison groups. Metabolomics analysis revealed that protein digestion and absorption (P = 0.0041), and amino acid metabolism pathways (P = 0.0052) were significantly enriched in the comparison between SBM + 1%YS and SBM groups. Correlation analysis further indicated that differential metabolites such as arginine and methionine exhibite a strong negative association with Edwardsiella.

Conclusion: Yeast enzyme hydrolysis slurry in soybean meal-based diets with partial fishmeal replacement enhanced the antioxidant capacity, reduced intestinal permeability, altered the abundances of intestinal microbiota and associated core metabolites. These positive changes collectively contributed to improved growth performance in largemouth bass.

Background: Transitioning to a high-grain (HG) diet significantly alters rumen fermentation by increasing the production of short-chain fatty acids (SCFAs) and lowering rumen pH, which may contribute to subacute ruminal acidosis (SARA) and damage to the ruminal epithelium. Rapid adaptation of rumen epithelium to these metabolic shifts is essential to maintain homeostasis, but the transcriptional mechanisms underlying this adaptation remain poorly understood.

Results: We analyzed the temporal progression of gene expression and metabolomic profile in rumen papillae collected during low-grain feeding (LG) and one week after transitioning to a HG diet (HG1), or four weeks after (HG4) in cows classified as susceptible or resistant to SARA. RNA sequencing identified 955 differentially expressed genes (DEGs) across time points, revealing a biphasic adaptation pattern. Early responses (HG1) showed moderate transcriptional changes, while HG4 was characterized by substantial transcriptional remodeling. Pathway analysis indicated three major functional categories affected during adaptation: cellular stress response, metabolic adaptation, and protein processing. Notably, sterol biosynthesis genes showed transient upregulation at HG1 followed by downregulation at HG4, coinciding with morphological changes in rumen wall thickness and n-butyrate concentration in rumen fluid. Correlation analyses comparing gene expression patterns and metabolite level changes triggered by the dietary transition revealed potential links between metabolic and transcriptional adaptation. Of particular interest, valerate levels at HG1 correlated with genes involved in tissue remodeling at HG4, implying that valerate may contribute to delayed epithelial responses. Next, transcriptional differences between SARA-susceptible and SARA-resistant animals included genes related to inflammation, cell structure, and metabolism that persisted across all time points, suggesting underlying intrinsic differences in SARA susceptibility that are present before and persist during dietary challenge. Key genes consistently differentially under-expressed in SARA-susceptible animals, CCDC196 and MYO7B, represent potential biomarkers for SARA predisposition. Finally, the SARA-resistant group showed a greater number of transcriptome-metabolome correlations, suggesting more coordinated epithelial responses to diet change compared to the SARA-susceptible group.

Conclusions: Our findings provide insights into the molecular mechanisms underlying rumen adaptation to HG diets and individual variation in SARA susceptibility, providing a basis for developing strategies to optimize dietary transitions in ruminant production systems.