In Vitro Assessment of Enteric Methane Emission Potential of Whole-Plant Barley, Oat, Triticale and Wheat

SIMPLE SUMMARY: There is an increasing interest in finding effective but economical strategies for mitigating enteric methane (CH(4)) emissions from ruminants. Small-grain cereal forages including barley, oat, triticale, and wheat, unlike maize, are widely grown in temperate locations and may be economical to use for ruminant production. However, the starch and fiber composition and concentrations of whole-plant cereal forages affect rumen degradability, and hence may cause differences in the CH(4) production potential among these forages. Therefore, the objective of this study was to determine the enteric CH(4) emission potential of various whole-plant cereals and evaluate whether the variability in emissions could be explained by variations in nutrient profiles, degradability, and rumen fermentation characteristics. The results indicate that feeding whole-plant oat forage to ruminants may decrease CH(4) emissions but adversely affect animal performance due to lower degradability, whereas barley forage may ameliorate emissions without negative effects on animal performance. ABSTRACT: The study determined in vitro enteric methane (CH(4)) emission potential of whole-plant cereal (WPC) forages in relationship to nutrient composition, degradability, and rumen fermentation. Two varieties of each WPC (barley, oat, triticale, and wheat) were harvested from two field replications in each of two locations in central Alberta, Canada, and an in vitro batch culture technique was used to characterize gas production (GP), fermentation, and degradability. Starch concentration (g/kg dry matter (DM)) was least (p < 0.001) for oat (147), greatest for wheat (274) and barley (229), and intermediate for triticale (194). The aNDF concentration was greater for oat versus the other cereals (531 vs. 421 g/kg DM, p < 0.01). The 48 h DM and aNDF degradabilities (DMD and aNDFD) differed (p < 0.001) among the WPCs. The DMD was greatest for barley, intermediate for wheat and triticale, and least for oat (719, 677, 663, and 566 g/kg DM, respectively). Cumulative CH(4) production (MP; mL) from 12 h to 48 h of incubation was less (p < 0.001) for oat than the other cereals, reflecting its lower DMD. However, CH(4) yield (MY; mg of CH(4)/g DM degraded) of barley and oat grown at one location was less than that of wheat and triticale (28 vs. 31 mg CH(4)/g DM degraded). Chemical composition failed to explain variation in MY (p = 0.35), but it explained 45% of the variation in MP (p = 0.02). Variation in the CH(4) emission potential of WPC was attributed to differences in DMD, aNDFD, and fermentation end-products (R(2) ≥ 0.88; p < 001). The results indicate that feeding whole-plant oat forage to ruminants may decrease CH(4) emissions, but animal performance may also be negatively affected due to lower degradability, whereas barley forage may ameliorate emissions without negative effects on animal performance.