Effects of strontium levels on in vitro fermentation parameters and microorganisms in the rumen of dairy cows

This study aims to investigate the effect of strontium chloride supplementation on the in vitro rumen fermentation characteristics and microorganisms of Dairy cows. Four fermentation substrates, including control (without strontium chloride supplementation, CK), strontium chloride supplementation (100, 400 and 1600 mg kg, CK, LH100 and LH1600, respectively) were incubated with rumen fluid in vitro. The results showed that in vitro gas production, microbial protein (MCP) concentration and volatile fatty acid (VFA) concentration was significantly higher in LH1600 than in LH100 and CK. pH was higher in CK than LH100, LH400 and LH1600. Moreover, higher species richness of rumen fluid was found in LH1600 than others. Higher relative abundance of horsej-a03, Sediminispirochaeta was detected in LH1600 than CK. Besides, higher relative abundance of Acetitomaculum was found in CK than other treatments. It is observed that 1600 mg kg DM strontium chloride could increase cumulative gas production, VFA concentration and MCP concentration by altering the relative abundance of horsej-a03, Sediminispirochaeta, Acetitomaculum . This study could provide a reference ratio of strontium chloride on rumen fermentation and bacterial composition via an in vitro test.

本研究旨在探究氯化锶（strontium chloride）添加对奶牛体外瘤胃发酵特性及瘤胃微生物的影响。本研究设置4组发酵底物，包括空白对照组（不添加氯化锶，标记为CK）与3个氯化锶添加组，添加剂量分别为100、400、1600 mg·kg⁻¹，对应标记为LH100、LH400及LH1600；将上述底物与瘤胃液共同进行体外孵育。结果表明，LH1600组的体外产气量、微生物蛋白（Microbial Protein, MCP）浓度与挥发性脂肪酸（Volatile Fatty Acid, VFA）浓度均显著高于LH100组与对照组。对照组的pH值显著高于LH100、LH400及LH1600组。此外，LH1600组的瘤胃液物种丰富度高于其余各组。LH1600组中horsej-a03与沉积物螺菌属（Sediminispirochaeta）的相对丰度显著高于对照组，而对照组中乙酸巨球菌属（Acetitomaculum）的相对丰度高于其余处理组。研究发现，添加剂量为1600 mg·kg⁻¹干物质的氯化锶可通过调控horsej-a03、沉积物螺菌属及乙酸巨球菌属的相对丰度，提升累积产气量、VFA浓度与MCP浓度。本研究通过体外试验可为氯化锶在瘤胃发酵及细菌群落组成方面的适宜添加比例提供参考依据。