The switch from wheat hay TMR to T-CS TMR had a significant effect on the bacterial community within
the rumen, which was also accompanied by a beneficial effect on rumen pH and digestibility of NDF and NDF
polysaccharides. This was reflected in similar NDF intake of the 2 groups, but higher milk fat and milk protein content, increase of 1.3% in ECM yield, and 5.34% in the production efficiency (ECM yield/intake) of cows fed the T-CS TMR compared with the control group. The mechanism by which the effect of T-CS is carried out in modifying the ruminal bacterial population warrants further research. Understanding these forces that influence rumen microbial populations may
contribute to future development of rumen microbial modulations toward improvement of cow performance.