Changes of Rumen Microbiota Density and Physicochemical Properties at Different pH北大核心CSCD

The aim of this experiment was to investigate the changes of rumen microbiota density and physicochemical properties at different pH. Five Holstein cows in dry milk period were selected as rumen fluid donors. Using in vitro method, five treatments were set according to the criteria of rumen acidosis, and the pH of culture medium was 6.5, 5.8, 5.5, 5.2 and 5.0, respectively, with five replicates in each treatment. After three hours of incubation, the changes of rumen microbiota density and physicochemical properties were measured. The results showed as follows: 1) with the decrease of pH, the rumen microbiota density showed a fluctuation change of first decreasing, then increasing and then decreasing, and the microbiota density in pH 5.8 treatment was significantly lower than that in pH 6.5 treatment (P<0.05). When pH was 5.2, the rumen microbiota density was the highest, which was significantly higher than that in the other treatments (P<0.05). 2) With the decrease of pH, the intracellular H+-ATPase activity in rumen microbiota was firstly increased and then decreased, but there was no significant difference among all treatments (P>0.05). 3) The intracellular ATP content in rumen microbiota was not significantly affected by different pH treatments (P>0.05). 4) With the decrease of pH, the intracellular protein content in rumen microbiota was gradually increased (P<0.05). 5) With the decrease of pH, the intracellular pH (pHi) and cellular transmembrane pH difference (ΔpH) in rumen microbiota were firstly increased and then decreased, and the pHi and ΔpH in pH 5.5 and 5.2 treatments were significantly higher than those in the other three treatments (P<0.05). 6) With the decrease of pH, the cell membrane permeability of rumen microbiota was gradually increased, except for pH 5.8 treatment, the other treatments were significantly higher than pH 6.5 treatment (P<0.05). In conclusion, the rumen microbiota can increase the intracellular H+-ATPase activity and protein content, consume ATP, and change pHi and ΔpH in response to external pH decline. When pH decreases to 5.5, the membrane permeability and pHi of rumen microbiota increase significantly, indicating that they are running to be subjected to more serious acid stress. The density of rumen microbiota fluctuates with the decrease of pH, and when pH decreases to 5.2, the density of rumen microbiota is the highest. © 2023 Authors. All rights reserved.