Barcelona, España
Two experiments were conducted to determinate the effects of several commercial lipases and essential oils on apparent biohydrogenation of linoleic (LA) and linolenic (LNA) acids and rumen fermentation. In a first experiment, in vitro incubations (Tilley & Terry, 1963) at two pH levels (6.4 and 5.6) in two replicated periods were used. Treatments were control; lipase 1 and 2 (0.4 and 4 μl/g DM); lipase inhibitor (0.4 and 2 mg/g DM); Oxy-propyl-thiosulphate (PTSO) (60 and 120 mg/l); Eugenol (EUG) and Cinnamaldehyde (CIN) (150 and 500 ml/l). In a second experiment, 8 dual-flow continuous culture fermenters (1,320 ml) were used in 3 replicated periods to study the effects of lipase 1 (4 μl/l), PTSO (90 mg/l) and CIN (250 mg/l) at two pH levels (6.4 and 5.6). Lipase 1, independently pH level and doses, increased the apparent biohydrogenation of LNA in the first experiment, however these results were not observed in the second experiment. PTSO inhibited the apparent biohydrogenation of LA and LNA and decreased the total VFA concentration at the two pH. The low pH inhibited the biohydrogenation of LA, increased the trans-10 18:1 isomer, and decreased the total VFA concentrations. Results indicated that effects of lipases observed in the Tilley & Terry incubation were not observed in long term fermenters, which suggests that microbial population was adapted to lipases. Reducing the pH inhibited the ruminal fermentation and increased the alternative pathway of ruminal biohydrogenation.
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