In vitro fermentation parameters and biohydrogenation of vegetable oils without glycerol

Glycerol combined with vegetable oils could limit biohydrogenation and enhance the reduction in methane production without depressing digestibility and microbial population. Three in vitro incubations were conducted to evaluate the effect of glycerol (0 or 150 g/kg DM) combined with three different diets: Tifton 85 hay without oil seeds (HWO), Tifton 85 hay + 80g of soybean oil/kg DM (HSO) and Tifton 85 hay + 80 g of linseed oil/kg DM (HLO) incubated for 0, 6, 12 and 24 h on fatty acid composition and ruminal fermentation parameters. Real-time PCR was used to quantify microbial population at 24 h. Methanogens, fibrolitic and lipolityc bacteria were expressed as a proportion of total rumen bacterial 16 S rDNA. Separately, kinetic of gas production was assessed at 2, 4, 6, 8, 10, 12, 14, 18, 22, 24, 36, 42 and 48 h. In vitro true digestibility (IVTD) and CH4 (%/g DMD) production were evaluated at 48 h. The experimental design for fatty acid composition and ruminal parameters was a randomized block in a factorial arrangement 2 x 3 x 4, involving the following factors: glycerol (2), diets (3) and time (4). Microbial quantification, IVTD and CH4 were evaluated with the same design but without time as a factor. The pH value and ammonia (NH3-N) concentration were lower in HWO compared with HSO and HLO diets, regardless of glycerol addition (P0.05). Among all cellulolytic bacteria, Fibrobacter succinogenes was the most sensitive to the addition of vegetable oil in the diet (P0,05). As bactérias Fibrobacter succinogenes foram mais sensíveis a adição de óleos vegetais entre todas as bactérias celulolíticas (P<0,05). A DVIV e a produção de CH4 foram inferiores nas dietas FOS com adição de glicerol e na dieta FOL independente da adição de glicerol (P