Effect of Different Level of Psyllium Supplementation to Horse Diet on in vitro Fermentation Parameters and Methane Emission

The purpose of this study was to determine the effect of psyllium addition to horse diets on methane emissions and digestion parameters by in vitro digestion technique using horse feces as inoculum. The effect of 0 (control group), 5, 10, 20 and 40 g/kg DM (Dry matter) (treatment groups) psyllium (Psyllium Husk, Solgar, UK) supplementations to horse diet were determined on in vitro total gas and methane production, metabolisable energy (ME), organic matter digestion (OMD), ammonia nitrogen (NH3-N), short chain fatty acids (SCFA) and pH value. In vitro digestibility technique was performed with using glass syringes of 100 ml volumes (Model Fortuna, Germany) at 39.0±0.2°C for 24 hour incubation. In the study, in vitro total gas production was linearly decreased in treatment groups (up to 130 ml/g DM) compared to control group (181 ml/g DM) (P<0.001). Inclusion of psyllium to horse ration decreased methane production up to 35% (P≤0.01). The ME, OMD and SCFA levels of horse diet affected by the psyllium supplementation (P<0.01). Addition of psyllium at the levels of 5, 10, 20 and 40 g/kg DM did not have an effect on NH3-N and pH (P>0.05). Consequently, it was demonstrated that psyllium, which use commonly in constipated horses because of laxative efficacy, reduced methane emission as another positive effect in horses. Although psyllium reduced methane emission, it had adverse effects on in vitro digestibility of horse ration. However, it was considered that further investigations are necessary to understand the effects deeply by doing the in vitro or in vivo digestion trials with lower doses or psyllium is not suitable to use in healthy horses for a long time.