Supplementing Propionibacterium acidipropionici P169 does not affect methane production or volatile fatty acid profiles of different diets in in vitro rumen cultures from heifers

Effects of Propionibacterium acidipropionici P169 on gas, methane (CH4) production and volatile fatty acids in in vitro rumen cultures were studied. Ground barley (Experiment 1), mixed forage (Experiment 2) or mixed concentrate-forage (Experiment 3) served as substrates. Three doses of P169 were used in Experiments 1 and 2 [1.2 x 10(4); 1.2 x 10(6); 1.2 x 10(8) colony forming unit (CFU)/mL], while two doses (2.4 x 10(6); 2.4 x 10(8) CFU/mL) were used in Experiment 3. In Experiment 1, P169 increased (P < 0.05) gas production at 6-12 h and CH4 (mL/g diet dry matter) at all times. In Experiment 2, CH4 was increased at 6 h (P < 0.01). At 12 h, propionate declined (P < 0.01) in Experiment 1 and increased at 48 h in Experiment 3. The inability of P169 to increase propionate and its lack of persistence in mixed ruminal cultures may account for its inability to alter CH4 production.