Abstract
Simple SummaryThere is an increasing interest in finding effective but economical strategies for mitigating enteric methane (CH4) 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 CH4 production potential among these forages. Therefore, the objective of this study was to determine the enteric CH4 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 CH4 emissions but adversely affect animal performance due to lower degradability, whereas barley forage may ameliorate emissions without negative effects on animal performance.The study determined in vitro enteric methane (CH4) 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 CH4 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, CH4 yield (MY; mg of CH4/g DM degraded) of barley and oat grown at one location was less than that of wheat and triticale (28 vs. 31 mg CH4/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 CH4 emission potential of WPC was attributed to differences in DMD, aNDFD, and fermentation end-products (R2 ≥ 0.88; p < 001). The results indicate that feeding whole-plant oat forage to ruminants may decrease CH4 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.
Highlights
Enteric methane (CH4 ) emissions from ruminants are estimated at 1.6 to 2.7 gigatons of carbon dioxide equivalent (CO2 e) per year, accounting for 3% to 5% of the 49 Gt total CO2 e produced globally by all sectors [1]
Oat, triticale, and wheat grown in two locations and harvested as whole-plant forage varied in nutrient composition, which affected rumen degradability, fermentation, and CH4 emission potential
When CH4 was expressed relative to dry matter (DM) degraded (i.e., methane yield (MY)), differences were due to fiber degradation and fermentation end-products (GP, acetate, butyrate, and ammonia)
Summary
Enteric methane (CH4 ) emissions from ruminants are estimated at 1.6 to 2.7 gigatons of carbon dioxide equivalent (CO2 e) per year, accounting for 3% to 5% of the 49 Gt total CO2 e produced globally by all sectors [1]. Methane is a potent greenhouse gas and contributes to climate change [2], and there is increasing emphasis on reducing enteric CH4 emissions from ruminants. Ruminants consume forage-based diets, and improving the nutritional quality of forages enhances feed conversion efficiency and animal performance. CH4 production from animals may increase due to greater feed intake and ruminal degradation of high-quality forages. Grasslands have notable environmental benefits such as carbon storage [4]; low-quality forages are estimated to account for 75% of global ruminant CH4 emissions [5] CH4 produced per unit of animal product (i.e., a measure of intensity) typically decreases with improved animal performance (growing animals reach market weight sooner so less feed is required; fewer lactating dairy cows are needed to produce a given volume of milk) [3].
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