Effect of alkaline mineral complex buffer addition on milk performance, blood parameters, and rumen microbiota in early-lactation dairy cows

This study evaluated the effects of an alkaline mineral complex buffer (AMCB) in the diet on lactation performance, blood parameters, rumen fermentation, and microbial composition in early-lactation Holstein cows. In total, 30 Holstein cows (average parity 3.76 ± 0.48, milk in lactation day 22.45 ± 0.51) were randomly assigned to a control group (CON) or an experimental group (EXP) receiving 50 mL AMCB daily, providing 10 g sodium metasilicate, 5 g potassium bicarbonate, 0.5 mg zinc oxide, and 0.05 mg Ge-132 per cow. Cows supplemented with AMCB exhibited higher dry matter intake, milk production, fat-corrected milk yield, and energy-corrected milk yield, as well as increased lactose and milk protein concentrations and daily yields (<i>P</i> < 0.05) compared to the CON group. Notably, there was a significant reduction in somatic cell counts in the milk (<i>P</i> < 0.05). AMCB supplementation also led to a decrease in serum levels of aspartate aminotransferase and alanine aminotransferase (<i>P</i> < 0.05), while increasing rumen ammonia nitrogen concentrations (<i>P</i> < 0.05). A trend toward greater bacterial richness (Chao1, <i>P</i> = 0.06) was observed, with significant increases in <i>Prevotellaceae</i>_UCG-001 and <i>Ruminococcaceae</i>_NK4A214_group by d 30 (<i>P</i> < 0.05), and <i>Enterococcus</i> identified as a biomarker in the EXP group. These findings underscore that AMCB supplementation enhances production performance in dairy cows, mitigates liver function impairment, and stimulates the proliferation of protein-degrading bacteria in the rumen. This highlights AMCB's potential as a strategic dietary intervention, offering valuable guidance for optimizing nutritional management to support both metabolic health and productivity for early-lactation cows.IMPORTANCEEarly lactation is a critical period for dairy cows, characterized by high milk production demands and a heightened risk of subacute ruminal acidosis, which compromises rumen function, fiber digestion, and overall productivity. While research on buffering agents has predominantly focused on monogastric animals or single-agent applications, the role of composite buffers in early-lactation dairy cows remains underexplored. Our study demonstrated that supplementation with an alkaline mineral complex buffer (AMCB) significantly improved milk yield and quality, increased the relative abundance of protein-degrading bacteria, reduced somatic cell counts, and enhanced liver function. These results provide compelling evidence supporting the strategic application of composite buffering agents to enhance lactational performance and metabolic health in dairy cows.