High methanogenic potential of sucrose compared with starch at high ruminal pH

Abstract

Summary The role of ruminal pH with respect to the expression of a differentiation in the methanogenic potential of easily fermentable carbohydrates was determined using the rumen simulation technique. The target pH at 21 h after feed supply was set to 6.0 and 7.0 through a specific buffer management. A basal diet was supplemented with crystalline sucrose or steamflaked maize starch. With sucrose instead of starch, the decline in fermenter fluid pH, 4 h after introducing new feed, was more pronounced at both buffer levels, and degradability of all nutrients, including fibre was higher too. At low pH, molar propionate proportion was higher with sucrose. Methane quantity depended on the combination of pH and source of easily fermentable carbohydrate as sucrose, compared with starch, enhanced methanogenesis (+40%), but only at the high pH. The concomitant increase in organic matter degradability with sucrose at high target pH did not completely explain this phenomenon, as the effects on methane were still significant when related to apparently fermented organic matter. However, differences caused by pH and carbohydrate type decreased when methane was related to degraded fibre, suggesting that there was a mutual supportive effect of high pH and sucrose on fibre degradation.

Effect of feeding dried high-sugar ryegrass (‘AberMagic’) on methane and urinary nitrogen emissions of primiparous cows

“…In case ruminal pH is lower when feeding a high-WSC cultivar than when feeding a low-WSC cultivar, ruminal methanogenesis should decline. Under this condition, sugars have a rather low CH 4 emission potential, which is similar to that of starch (Hindrichsen and Kreuzer, 2009). The methanogens are susceptible to pHo6 (Hu et al, 2005).…”

“…Replacing fiber with starch is expected to decrease enteric CH 4 emissions (Moss et al, 2000). By contrast, sugars might have a higher methanogenic potential than starch or even fiber (Ellis et al, 2012;Hindrichsen et al, 2005), but this presumably only when a high ruminal pH is maintained (Hindrichsen and Kreuzer, 2009). …”

Enteric and manure-derived methane and nitrogen emissions as well as metabolic energy losses in cows fed balanced diets based on maize, barley or grass hay

“…In this study, the use of mixed diets containing considerable proportions of poor quality forages (stover and straw) might have prevented this decline in ruminal pH, especially since the concentrate was fed to the animals in several portions over the day. It has been shown before that the expression of specific carbohydrate effects requires a drop in ruminal pH (Hindrichsen and Kreuzer, 2009). Further, it was shown that starch-based diets can indeed have a rather high methanogenic potential when related to DM intake (Hindrichsen et al, 2005).…”

“…Such high-concentrate diets support the formation of propionate, which might act competitively as a hydrogen sink in the rumen compared with CH 4 (Moss et al, 2000). Still, CH 4 is also formed from non-structural carbohydrates with the amount of CH 4 depending on ruminal degradability (starch) and carbohydrate type (starch v. sugars; Hindrichsen et al, 2005;Hindrichsen and Kreuzer, 2009). …”

Effects of Degradable Protein and Non-Fibre Carbohydrates on Microbial Growth and Fermentation in the Rumen Simulating Fermenter (Rusitec)

“…Inc., Cary, NC, USA) according to a randomized complete block design (blocking by incubation) (Hindrichsen and Kreuzer, 2009). The model included treatments (NFC and RDP) and the interaction between NFC and RDP as fixed effects and incubation period (block) as a random effect.…”