PSXIV-21 Effect of high-tannin sorghum grain on rumen fermentation and methane production in vitro

Abstract

Tannins are natural compounds with potential to reduce enteric methane (CH4) emissions in ruminants. High-tannin sorghum (HTS) varieties are cultivated in different regions of the world, including Mexico. The objective of this study was to evaluate the effects of HTS on rumen fermentation and CH4 production using a batch culture system. The experiment was set up as a completely randomized block design using a 3 × 5 factorial arrangement with 3 grains [HTS, low-tannin sorghum (LTS), and corn, with 19.6, 0.07 and 0 g of condensed tannins (CT)/kg dry matter (DM) respectively] and 5 grain to forage (alfalfa hay) proportions (20:80, 40:60, 60:40, 80:20 and 100:0). Data were analyzed using the MIXED procedure of SAS. Contrasts were used to determine linear and quadratic effects of grain:forage proportions. A decrease of 2.96% in CH4 concentration was observed for sorghum treatments compared to corn (P < 0.01). However, HTS and LTS were not different from each other (P = 0.76). Furthermore, CH4 production (mL/d) decreased (P < 0.01) by 19.13 and 8.53% with HTS compared with corn and LTS respectively. This reduction was associated with a decrease (P < 0.01) of 14.52 and 10.04% in total gas production with HTS as compared to corn and LTS. Both, CH4 and gas production decrease, were associated with reduced DM digestibility for HTS, which can be a negative effect of CT in HTS. Sorghum treatments produced 14.56% less CH4 (mL/g DM; P < 0.01) than corn. This was partially explained by a 7.98% decrease in DMD with sorghum treatments. As expected, gas production linearly increased and rumen pH linearly decreased with increasing levels of grain (P < 0.01). In conclusion, HTS had no advantage over LTS in terms of CH4 production. Nonetheless, sorghum grain, substituted for corn, can be an option to decrease CH4 production in ruminants, but digestibility might be compromised.