The use of quantitative real time polymerase chain reaction to quantify some rumen bacterial strains in an in vitro rumen system

The aim of this work was to quantify four rumen bacterial strains (Butyrivibrio fibrisolvens, Ruminococcus albus, Streptococcus bovis, Megasphaera elsdenii) in an in vitro batch rumen fermentative system by quantitative real time polymerase chain reaction (qPCR). The experiment was a 2×2 factorial arrangement with two types of liquid rumen, collected from dairy cows (DC) and fattening bulls (FB) and two types of fermentation substrate (forage:concentrate ratios, 75:25 and 25:75) and was replicated in two fermentation runs. Fermentation fluids from FB compared to those from DC had lower pH, higher total VFA concentrations (averages of 0 and 24 h samplings, 6.70 vs 7.04 and 72.6 vs 42.7 mmol/l P<0.001) and contained less acetic (P=0.014) and more propionic (P<0.01) and butyric (P=0.029) acids. The two types of substrates incubated produced very small differences in the end fermentation products. B. fibrosolvens concentrations were higher (P<0.001) in the DC fermentation fluids compared to that from bulls (averages of 0 and 24 h sampling times, 3.47 vs 1.38 x109 copies /mL), while M. elsdenii was detected only in FB fermentation fluids. R. albus and S. bovisconcentrations were not different between the two types of rumen liquid. With the only exception for B. fibrosolvens, bacteria strains considered in this study increased their concentrations in the fermentation fluid during the 24 h of in vitro incubation.