The Effect of Dietary Fermented Grape Pomace Supplementation on In Vitro Total Gas and Methane Production, Digestibility, and Rumen Fermentation

The aim of this study comprises the effect of fermented grape pomace (FGP) in experimental total mixed rations (TMR) at different rates (0, 7.5%, 15%, and 22.5%) on the in vitro cumulative gas production (6th, 12th, 18th and 24th hours), methane production, ruminal fermentation values, pH and ammonia-nitrogen and straight and branched short-chain fatty acids (SCFA and BCFA) concentration. The method of in vitro total gas production was carried out in glass syringes. Ruminal in vitro methane production linearly decreased by adding up to 22.5% FGP in experimental TMR (p < 0.05). The molarities of acetic, propionic, butyric, and valeric acids in the in vitro fermentation fluid linearly decreased with the addition of FGP to TMR (p < 0.05). FGP up to 22.5% in experimental TMRs decreased the molarity of iso-valeric acid and iso-butyric acid from BSCFAs (p < 0.05). As a result, it was concluded that the use of FGP, containing a low level of total condensed tannins (TCTs), up to 22.5% in the experimental TMR based on dry matter (DM) did not adversely affect the in vitro ruminal fermentation value and had an anti-methanogenic effect. In addition, some SCFA (acetic, propionic, butyric, and valeric acids) molarities and iso-acid BSCFA (iso-butyric and iso-valeric acid) did not change up to 15% rate of FGP in the ration. Still, these values decreased by using a 22% rate of FGP. The dose-dependent effect of FGP on ruminal iso-acids has been associated with the ability of TCTs to inhibit ruminal protein degradation partially.