Effects of different fiber levels of energy feeds on rumen fermentation and the microbial community structure of grazing sheep

Effect of citric waste fermented with yeast waste pellet and roughage-to-concentrate ratio on gas production, digestibility, and fermentation characteristics using an in vitro gas production technique

BACKGROUND

Agro-industrial byproducts offer promising solutions for reducing feed costs and mitigating environmental pollution. Efficient waste management through recycling and reuse not only minimizes environmental impact but also opens avenues for innovative animal feed products. The objectives of this research were to determine whether increasing the roughage-to-concentrate diet (R: C) ratio and adding citric waste fermented with yeast waste pellets (CWYWP) would improve gas production, digestibility, and fermentation outcomes. A 2 × 4 factorial experiment was conducted using a completely randomized design. The first factor comprised two levels of R: C ratios: 60:40 and 40:60. Rice straw was used as a roughage source. The second factor involves four levels of CWYWP supplementation (as a top-dressed substrate supplement) at 0%, 2%, 4%, and 6% dry matter (DM), respectively.

RESULTS

A significant interaction between CWYWP level and R: C ratio was observed for cumulative gas production, with 2% and 4% CWYWP increasing gas volumes under the 40:60 ratio, peaking at 113.10 mL/0.5 g at 4% inclusion. Similarly, a significant interaction was found for in vitro digestibility at 24 h, where 4% CWYWP under 40:60 R: C significantly enhanced in vitro organic matter digestibility and in vitro dry matter digestibility compared to other levels. CWYWP supplementation elevated ammonia-nitrogen concentrations at both 2 and 4 h and slightly increased ruminal pH at 4% and 6% inclusion, with all pH values remaining within the physiological range. Volatile fatty acid profiles shifted toward higher propionate and lower acetate-to-propionate ratio, particularly at 6% CWYWP under 40:60 R: C, indicating improved glucogenic fermentation.

CONCLUSION

These findings suggest that CWYWP can be safely included at up to 4% in high-concentrate diets without impairing in vitro ruminal fermentation or digestibility.

Exploring the cecal microbial community associated with fat deposition in sheep and its possible pathways of action

Fat deposition is a crucial economic trait during sheep growth and development, closely linked to economic returns. Current research on sheep's digestive tract predominantly focuses on the rumen, but the composition of the cecal microbiota and its relationship with host fat deposition remains largely unexplored. In this study, we sequenced the cecal microbiota of 60 Hu sheep, exhibiting marked differences in traits. The most abundant species in the sheep cecum were Firmicutes and Bacteroidota. Statistical analyses revealed significant differences in microbial community structures among different fat-deposition groups (P < 0.05). Using a random forest regression model and linear regression, 15 microbial biomarkers, including Lachnospiraceae_NK3A20_group, Turicibacter, and Bacteroides, were identified as key contributors to fat deposition. Additionally, volatile fatty acids (VFAs) in the cecum and biochemical indices in serum were measured. Acetic acid was the most abundant VFA in the cecum, while isobutyric acid levels were significantly higher in the low-fat group than in other groups (P < 0.05). Serum triglyceride (TG) levels were significantly higher in the high-fat group (P < 0.05). Correlation analysis revealed a significant association between Lachnospiraceae_NK3A20_group and acetic acid levels, as well as between TG levels and fat deposition traits (P < 0.05). TG levels were negatively correlated with acetic acid concentrations (P < 0.05). These findings suggest that the cecal microbiota influences fat deposition in sheep, potentially via the VFAs-TG metabolic pathway.

IMPORTANCE

Compared with muscle development, fat deposition consumes more energy, and controlling the fat deposition process can effectively reduce energy waste. Current research on rumination mainly focuses on the rumen but lacks research on the hindgut. This study identifies differences in the cecal microbiota of sheep with varying fat deposition levels and highlights significant correlations between specific microorganisms, cecal metabolites, and host traits. Therefore, the regulation of cecal microorganisms can help improve the fat deposition characteristics of sheep.