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.