PSVIII-17 - Effect of high-tannin sorghum grain on in vitro rumen fermentation and methane production

The objective was to evaluate the potential of methane (CH4) mitigation of high-tannin sorghum (HTS) varieties (V). The experiment was arranged as a completely randomized block design with a 7 × 2 factorial arrangement of treatments, including 6 HTS varieties (BRS72, Dekalb; 81G67, Dupont-Pioneer; QL-BR95, Lucava; 6001, ACA; NYX, Unisem; Red Bird, Warner Seeds; 20.1±3.2 g/kg condensed tannins), a low tannin sorghum (LTS, 0.3 g/kg condensed tannins) and two levels of polyethylene-glycol (PEG; 0 and 1 g). Three independent batch culture runs were conducted using a basal diet (0.5 g) containing 72% sorghum, 18% corn stover and 10% soybean meal. Total gas production (TGP), CH4 production, gas production kinetics and dry matter digestibility (DMD) were evaluated. Data were analyzed with R studio 1.4.1106 using a mixed model and the Tukey instruction for mean comparison. Interaction (V × PEG) was not significant (P = 0.16) for DMD. However, DMD decreased (P > 0.05) 6.1 percentage units with HTS varieties compared to LTS. Furthermore, PEG increased (P > 0.05) DMD by 1.78 percentage units. The V × PEG interaction tended to be significant for TGP (P = 0.09; mL/g DM), where sorghum 81G67 + PEG showed the lowest gas production (486 mL/g DM). Kinetics of gas production were also affected. Fermentation rate was higher (P > 0 .05) for the LTS variety (0.0373 %/h) and lower (P > 0.05) for sorghum 81G67 (0.0317 %/h), while maximum volume of gas was 5.9% higher (P > 0.05) when PEG was included. Methane concentration (%) was lowest (P < 0.05) with QL-BR95 sorghum but CH4 production (mL/g DM) was not affected (P = 0.38) by sorghum variety. Methane concentration and production increased (P > 0.05) 8.9 and 4.1% respectively with PEG inclusion. In conclusion, HTS negatively affected digestibility and rumen fermentation while PEG minimized such effects. Sorghum grain varieties with high tannin content had negligible effects on rumen methanogenesis.