Effect of Propionibacterium freudenreichii in diets containing rapeseed or flaxseed oil on in vitro ruminal fermentation, methane production and fatty acid biohydrogenation

Abstract

The objectives of the present study were to determine the effect of inoculating Propionibacterium freudenreichii subsp. shermanii ATCC 8262 (1 × 109 colony-forming units per vial) in a barley silage-based diet supplemented with flaxseed oil or rapeseed oil (60 g/kg DM), on in vitro proportions and yield of volatile fatty acids, methane production and fatty acid (FA) biohydrogenation. Total volatile fatty acid production (mM) and proportions of individual FAs were not affected (P ≥ 0.10) by P. freudenreichii. Similarly, propionibacteria had little impact on FA biohydrogenation, resulting only in an increased accumulation (P < 0.01) of C18:1 cis-15 (g/kg total FA) at 6 h of incubation, compared with the control (CON). Compared with the CON, an increased (P < 0.01) accumulation of vaccenic acid was observed at 48 h in all oil-containing treatments, regardless of the oil type. Similarly, the apparent biohydrogenation of flaxseed oil resulted in an increased (P ≤ 0.04) accumulation of conjugated linoleic acid cis-9, trans-11, compared with all other treatments. Additionally, flaxseed oil produced a greater (P ≤ 0.01) accumulation of beneficial biohydrogenation intermediates (C18:2 trans-11, cis-15; C18:1 cis-15 and vaccenic acid), reflecting its ability to produce a more desirable FA profile than that of rapeseed oil or CON. The inability of P. freudenreichii subsp. shermanii ATCC 8262 to alter ruminal fermentation in a manner that lowered methane production, along with only minor effects on FA profiles through biohydrogenation, suggests that the biological activity of this strain was not realised under in vitro batch-culture conditions.