Research Article: Lower Methane Emissions from Yak Compared with Cattle in Rusitec Fermenters

Date Published: January 11, 2017

Publisher: Public Library of Science

Author(s): Jiandui Mi, Jianwei Zhou, Xiaodan Huang, Ruijun Long, Hauke Smidt.


Globally methane (CH4) emissions from ruminant livestock account for 29% of total CH4 emissions. Inherited variation about CH4 emissions of different animal species might provide new opportunity for manipulating CH4 production. Six rumen-simulating fermenters (Rusitec) were set up for this study lasting for 16 d. The diet consisted of forage to concentrate ratio of 50:50 with barley straw as the forage. Treated vessels were supplied with rumen fluid from yak or cattle (3 vessels per animal species). Microbial growth was measured using 15N as a marker. The microbial community structure from liquid- and solid-fraction of each vessel was determined based on the 16S rRNA genes targeting both bacteria and archaea with MiSeq platform. CH4 yield was lower when the inoculum used from yak than that from cattle (0.26 and 0.33 mmol CH4/g dry matter intake, respectively). Lower H2 production was observed in Rusitec fermenters with rumen fluid from yak compare with that from cattle (0.28 and 0.86 mmol/d, respectively). The apparent digestibility of neutral detergent fiber, the isovalerate percentage with respect to the total amount of volatile fatty acids, the hydrogen recovery, and the proportion of liquid-associated microbial nitrogen derived from ammonia-nitrogen were higher in Rusitec fermenters incubated with rumen fluid from cattle than that from yak. The relative abundances of methanogens were no difference between two animal species. We hypothesize that more H2 production contributes to the higher methane emissions in cattle compare with yak.

Partial Text

Methane (CH4) accounts for 11% of total greenhouse gas (GHG) emissions in China. Almost 21% of CH4 emissions are due to enteric fermentation in ruminant livestock industry [1, 2]. The Global Warming Potential (GWP) of CH4 for a time horizon of 100 years is 28-fold that of CO2 [3]. Enteric CH4 emissions also represent a 2 to 12% loss of gross energy intake [4]. Many ways to manipulate enteric CH4 emissions have been developed, including 4 broad categories: feeds and feeding management, rumen modifiers, genetics and other management strategies [5]. Investigating animals that produce lower CH4 might lead to improving livestock systems through modifying rumen fermentation and reducing CH4 emissions from other livestock [6–8].

Average values of effluent volume, pH, and substrate digestibility were summarized in Table 2. Because our main aim was to investigate the difference between yak and cattle species, a similar pH under two treatments would maintain a stable environment (Table 2). No differences in effluent volume, apparent disappearance of dry matter (DM), organic matter (OM), and neutral detergent fiber (NDF) were found between the two species (P>0.05).




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