Effect of quebracho condensed tannin extract on fecal gas flux in steers

Naturally occurring gaseous by-products of ruminant production-carbon dioxide (CO₂ ), methane (CH₄ ), and nitrous oxide (N₂ O)-can negatively affect the environment. Along with enteric fermentation, manure on pasture is among the most significant contributors to non-CO₂ emissions. Condensed tannins, a group of naturally occurring phenolic compounds, can alter the route of nutrient excretion and interact with microbes, suggesting they are a plausible feed additive for reducing excreta gas emissions. We evaluated how quebracho (Schinopsis balansae) tannin extract fed at 0, 15, 30, and 45 g kg^-1 of dry matter (DM) within a roughage-based diet affected fecal gas emissions at multiple locations (College Station and Stephenville, TX) during two periods corresponding to winter and spring. During both periods, CO₂ , CH₄ , and N₂ O fluxes were determined using the vented-static chamber methodology over 39 d, and cumulative emissions were calculated. A random coefficients model with animal nested within dietary treatment and period as the random factor was analyzed by location due to the presence of collinearity with soil parameters within periods. Daily CO₂ flux was influenced by soil moisture and temperature (r = .34; P < .01), whereas CH₄ and N₂ O were associated with soil moisture. Cumulative gas production confirmed a dietary effect for CO₂ and gross CO₂ equivalent at the College Station site (P ≤ .001), demonstrating a linear reduction as quebracho inclusion increased. Variance partitioning indicated that dietary treatment and seasonal period likely influenced animal digestive and metabolic parameters. Within specific environments, quebracho supplementation may assist in reducing fecal gas emissions.