Xiaoxiao Du

To investigate the effects of 5-hydroxymethylfurfural (5-HMF) on ruminal fermentation characteristics and bacterial community structure, 5-HMF was supplemented at the levels of 0, 7500, and 30,000 mg/kg DM under two dietary concentrate-to-roughage ratios (20:80, T1; 80:20, T2) in in vitro rumen incubation, mainly focusing on gas production, fermentation parameters, nutrient digestibility and bacterial community. The results showed that 24 h gas production (GP₂₄), 72 h gas production (GP₇₂), the gas production rate (c) and dry matter digestibility (DMD) in T2 were higher than those in T1 (p < 0.01). With increasing levels of 5-HMF supplementation, GP₇₂ and asymptotic gas production (B) increased linearly and quadratically (p < 0.05). T2 also had a higher butyrate concentration and a lower acetate/propionate (A/P) ratio than T1 (p < 0.05). With the increase in 5-HMF supplementation level, ruminal ammonia nitrogen (NH₃-N) concentration showed a quadratic response. In contrast, the concentrations of total volatile fatty acids (TVFAs), acetate and isobutyrate decreased linearly. Propionate concentration showed linear and quadratic decreasing trends, while the A/P ratio exhibited linear and quadratic increasing trends (p < 0.05). The supplementation of 5-HMF at 30,000 mg/kg DM reduced propionate and isobutyrate concentrations under both dietary conditions (p < 0.05). No differences were observed in the alpha diversity indices of the bacterial community among different 5-HMF levels or substrates (p > 0.05). PCoA and PERMANOVA revealed that community structure differed between the 7500 mg/kg DM group and the 0 mg/kg DM group in the T1 diet (p = 0.011), whereas no difference was detected among T2 treatments. LEfSe revealed that 6 and 13 differential bacterial taxa were identified in T1 and T2 at the 5-HMF level of 7500 mg/kg DM, respectively. Correlation analysis revealed that, in T1, GP₇₂ was positively correlated with Pseudomonadota, and the A/P ratio was positively correlated with fibrolytic taxa including Rikenellaceae_RC9_gut_group and Christensenellaceae_R-7_group. In T2, c was positively correlated with Fibrobacterota and Fibrobacter, while NH₃-N was positively correlated with Desulfovibrio, indicating diet-specific microbial associations with rumen fermentation (p < 0.05). In conclusion, the high-concentrate diet exhibited stronger rumen fermentation activity. 5-HMF exerted diet-specific effects: In the low-concentrate diet, 5-HMF at 7500 mg/kg DM enriched fibrolytic microbes and shifted fermentation toward an acetate-type pattern. In the high-concentrate diet, it modulated hydrogen-metabolizing bacteria while selectively enriching Pseudomonadota capable of participating in carbohydrate metabolism. The 30,000 mg/kg DM level inhibited rumen fermentation. The findings provide a theoretical reference for the application of 5-HMF in ruminant feeds. However, further in vivo trials are required to validate its effects, and future studies with refined dose gradients based on realistic 5-HMF concentrations in feedstuffs are needed to comprehensively evaluate its efficacy and safety.

Grain byproducts can serve as cost-effective alternatives to corn, but may lead to reduced production performance and increased greenhouse gas emissions. This study aimed to investigate the effects of replacing corn with the grain byproducts (wheat bran, sprayed corn bran) subjected to bacterial-enzymatic fermentation treatment or not in Hu sheep, mainly focusing on production performance, energy-nitrogen metabolism, rumen fermentation and greenhouse gas emissions. A total of fifty-four 6-month-old Hu sheep were divided into three groups, with 6 pens per group and 3 sheep per pen, and then randomly allocated to one of the three dietary groups for 60 days, i.e., a control group (CON), a group (RC) that corn was partially (~42%) replaced with grain byproducts, and a group (BF) that corn was partially replaced by fermented grain byproducts. Compared with the CON group, the RC group showed numerically lower rumen total volatile fatty acid (TVFA) concentration and its propionate proportion, nitrogen retention content (NR; −10.22%) and its retention ratio (NR/NI decreased by 4.27 percentage points, absolute reduction from 24.30% to 20.04%), corresponding to a relative decrease of 17.6%.) as well as a numerically reduced net profit (−2.18%) with a decreased feed price (−¥0.16/kg TMR). Meanwhile, the RC group showed a significant increase in the relative abundance of Methanobrevibacter (p < 0.05), accompanied by numerically higher daily methane emissions (+6.14%) and emission intensity (+4.08%), although these methane-related differences did not reach statistical significance (p > 0.05). Compared to the RC group, the BF group resulted in a numerical increase in feed price (+¥0.03/kg TMR), net profit (+27.93%), TVFA concentration, propionate proportion, NR (+28.17%), NR/NI (an increase of 5.38 percentage points), the relative abundance of Prevotella, Shuttleworthia and Succinivibrio as well as the decrease of fecal nitrogen (FN; −12.29%), daily methane emissions (−8.75%), emission intensity (−5.83%) and the relative abundance of Methanobrevibacter. In summary, replacing dietary corn by 42% with wheat bran and sprayed corn bran numerically reduced formula cost and nitrogen utilization, while increasing methane emissions and methanogens abundance, without significantly affecting growth performance. This combination led to no improvement in economic returns for fattening Hu sheep. Bacterial-enzymatic fermentation treatment of these byproducts could mitigate these drawbacks, being superior energy-nitrogen metabolism and lower greenhouse gas emissions intensity, presenting a potential strategy for cost reduction and efficiency enhancement. Further research with larger sample sizes is warranted to confirm these findings and support broader application.