To develop sustainable strategies for mitigating ruminal methanogenesis and improving nitrogen efficiency in dairy systems, this study investigated how low-dose tannic acid (T), tea polyphenols (TP), and their combination (T+TP; 50:50) modulate rumen microbiota and function. A sample of Holstein cows were given four dietary treatments: (1) control (basal diet); (2) T (basal diet + 0.4% DM tannic acid); (3) TP (basal diet + 0.4% DM tea polyphenols); and (4) T+TP (basal diet + 0.2% DM tannic acid + 0.2% DM tea polyphenols). We comprehensively analyzed rumen fermentation, methane production, nutrient digestibility, milk parameters, and microbiota dynamics. Compared with the control group, all diets supplemented with additives significantly reduced enteric methane production (13.68% for T, 11.40% for TP, and 10.89% for T+TP) and significantly increased milk protein yield. The crude protein digestibility significantly increased in the T group versus control. The results did not impair rumen health or fiber digestion. Critically, microbiota analysis revealed treatment-specific modulation: the T group showed decreased Ruminococcus flavefaciens abundance, while all tannin treatments reduced abundances of Ruminococcus albus and total methanogens. These microbial shifts corresponded with functional outcomes—most notably, the T+TP synergy drove the largest reductions in rumen ammonia-N (34.5%) and milk urea nitrogen (21.1%). Supplementation at 0.4% DM, particularly the T+TP combination, effectively enhances nitrogen efficiency and milk protein synthesis while reducing methane emissions through targeted modulation of key rumen microbiota populations, suggesting potential sustainability benefits linked to altered rumen fermentation.

This study examined the effects of alfalfa silage versus alfalfa hay in a total mixed ration (TMR) on milk yield, rumen fermentation, and nutrient digestibility in dairy cows. Hydrolyzed tannins (HT) were supplemented individually to assess changes. Thirty-two multiparous Holstein cows (DIM: 94 ± 8 d; milk yield: 41 ± 2 kg) were assigned to four treatments in a 2 × 2 factorial design: basal diet (alfalfa hay, H, or alfalfa silage, S) and additive (control, C, or 100 g/d HT, T). Production performance, rumen fermentation, nutrient digestibility, and blood metabolites were evaluated. Compared with group H, group S had a 0.16% higher milk protein percentage and significantly higher fat-corrected milk yield, milk fat percentage, fat-to-protein ratio, total solids, and milk urea nitrogen. After feeding, the ST group had increased ruminal pH. HT supplementation significantly decreased ruminal NH₃-N levels (p < 0.05) and increased microbial crude protein (MCP) content (p < 0.05). Group H showed no significant changes, and the effects of HT were less evident in hay-fed cows than in silage-fed cows. In summary, alfalfa silage feeding increased ruminal microbial populations, while HT supplementation mitigated the post-feeding decline in ruminal pH. Considering the relatively small sample size (n = 32), the results should be viewed as indicative rather than conclusive, and future studies with larger cohorts will be valuable to confirm and extend these findings.

This study evaluated the effects of rumen-protected chromium-nicotinic acid (RPCNA) supplementation on lactation performance, nutrient digestion, ruminal fermentation, serum biochemical parameters and antioxidant in lactating water buffaloes under conditions of a critical thermal comfort index (TCI). Healthy lactating water buffaloes (milk yield = 5.96 ± 0.21 kg; parity = 2.96 ± 0.15, mean ± SD) were randomly assigned to four groups, which were the control (without RPCNA), and three treatment groups designated as RPCNA2, RPCNA4, and RPCNA6, with 0, 2, 4, and 6 mg/(d·head) of RPCNA, respectively. During a 56-day experimental period, the average temperature was 29 °C with an average TCI of 40.60, indicating a critical state of environmental stress. The results showed that the addition of RPCNA to the diet had no significant effect on the apparent digestibility of nutrients, lactation performance, and dry matter intake in lactating water buffaloes. However, RPCNA supplementation positively influenced rumen fermentation, reducing ammonia nitrogen (NH₃-N) concentrations and promoting microbial protein synthesis. Supplementation with RPCNA4 and RPCNA6 decreased rumen NH₃-N levels by 48.3% and 36.4%, respectively, while RPCNA4 increased isobutyrate concentrations. This demonstrates that the coating technology does not provide 100% rumen protection. Serum analysis revealed that RPCNA significantly increases total antioxidant capacity (T-AOC). Additionally, the supplementation of 4 mg/(d·head) of RPCNA, improved serum glutathione peroxidase (GSH-Px) activity and reduced malondialdehyde (MDA) levels. These findings suggest that moderate doses of RPCNA supplementation can improve antioxidant status and rumen nitrogen metabolism in lactating water buffaloes under critical state, without significantly altering milk production or composition.

Skatole (3-methylindole) is a primary malodorous compound emitted from livestock manure, posing significant challenges for odor control in intensive animal production. In this study, a skatole-degrading bacterial strain, designated hhy901, was isolated from fresh cattle manure and identified as Bacillus pumilus through polyphasic taxonomy, including 16S rRNA and gyrB gene phylogeny, morphological characterization, biochemical profiling, and whole-cell fatty acid analysis. Under an initial skatole concentration of 100 mg/L in Bacillus liquid medium, strain hhy901 removed 87.2% of skatole within 96 h, as determined by high-performance liquid chromatography (HPLC). Whole-genome sequencing revealed a genome of approximately 3.60 Mb with a GC content of 41.91%, encoding 3564 predicted protein-coding genes. Functional genomic annotation identified 39 genes associated with xenobiotic biodegradation and metabolism, including putative catechol dioxygenase, aldehyde dehydrogenase, and cytochrome P450 genes, which together suggest a potential skatole catabolic pathway. Furthermore, the genome harbored a broad repertoire of genes associated with resistance to heavy metals, disinfectants, and multiple antibiotic classes, indicating a potential for environmental stress adaptation. Virulence factor profiling predominantly identified genes related to nutrient acquisition and microbial competition, with only a single invasion-associated factor detected, suggesting a relatively low invasive pathogenic potential. However, the presence of multiple antimicrobial resistance determinants warrants cautious interpretation, and phenotypic validation of both degradation function and biosafety is required before environmental application. These results establish B. pumilus hhy901 as a promising microbial candidate for further development of bio-deodorization strategies in livestock production, pending functional and safety validation.