Lambs Fed Fresh Winter Forage Rape (Brassica napus L.) Emit Less Methane than Those Fed Perennial Ryegrass (Lolium perenne L.), and Possible Mechanisms behind the Difference

Abstract

The objectives of this study were to examine long-term effects of feeding forage rape (Brassica napus L.) on methane yields (g methane per kg of feed dry matter intake), and to propose mechanisms that may be responsible for lower emissions from lambs fed forage rape compared to perennial ryegrass (Lolium perenne L.). The lambs were fed fresh winter forage rape or ryegrass as their sole diet for 15 weeks. Methane yields were measured using open circuit respiration chambers, and were 22-30% smaller from forage rape than from ryegrass (averages of 13.6 g versus 19.5 g after 7 weeks, and 17.8 g versus 22.9 g after 15 weeks). The difference therefore persisted consistently for at least 3 months. The smaller methane yields from forage rape were not related to nitrate or sulfate in the feed, which might act as alternative electron acceptors, or to the levels of the potential inhibitors glucosinolates and S-methyl L-cysteine sulfoxide. Ruminal microbial communities in forage rape-fed lambs were different from those in ryegrass-fed lambs, with greater proportions of potentially propionate-forming bacteria, and were consistent with less hydrogen and hence less methane being produced during fermentation. The molar proportions of ruminal acetate were smaller and those of propionate were greater in forage rape-fed lambs, consistent with the larger propionate-forming populations and less hydrogen production. Forage rape contained more readily fermentable carbohydrates and less structural carbohydrates than ryegrass, and was more rapidly degraded in the rumen, which might favour this fermentation profile. The ruminal pH was lower in forage rape-fed lambs, which might inhibit methanogenic activity, shifting the rumen fermentation to more propionate and less hydrogen and methane. The significance of these two mechanisms remains to be investigated. The results suggest that forage rape is a potential methane mitigation tool in pastoral-based sheep production systems.

Invited review: Large-scale indirect measurements for enteric methane emissions in dairy cattle: A review of proxies and their potential for use in management and breeding decisions

“…Low-CH 4 -emitting microbial communities were associated with higher relative proportions of Fibrobacteres, Quinella ovalis, and other Veillonellaceae such as Selenomononas, in contrast to lower proportions of Ruminococcaceae, Lachnospiraceae, and other Clostridiales (Kittelmann et al, 2014;Wallace et al, 2014;Sun et al, 2015). Fibrobacteres, Quinella, and Selenomononas are broadly known to consume H 2 whereas Ruminococcaceae, Lachnospiraceae, and other Clostridiales produce H 2 during fermentation, and changes in the proportion of these populations would reduce the amount of H 2 available for methanogenesis.…”

“…The relationship between rumen methanogen abundance and methanogenesis is less clear when changes in enteric CH 4 emissions are modulated by diet or are a consequence of selecting phenotypes related to feed efficiency or MeY. Whereas in some reports, significant positive relationships were identified (Aguinaga Casañas et al, 2015;Arndt et al, 2015;Sun et al, 2015;Wallace et al, 2015), in many others, the concentration of methanogens was unrelated to methanogenesis (e.g., Morgavi et al, 2012;Kittelmann et al, 2014;Shi et al, 2014;Bouchard et al, 2015). Bouchard et al (2015) even reported a reduction in methanogens without a significant decrease in MeP for steers fed sainfoin silage.…”

“…Fibrobacteres, Quinella, and Selenomononas are broadly known to consume H 2 whereas Ruminococcaceae, Lachnospiraceae, and other Clostridiales produce H 2 during fermentation, and changes in the proportion of these populations would reduce the amount of H 2 available for methanogenesis. In the rumen, these microbial changes are biochemically associated with higher proportions of propionate (Kittelmann et al, 2014;Wallace et al, 2014;Sun et al, 2015).…”

The Type of Forage Substrate Preparation Included as Substrate in a RUSITEC System Affects the Ruminal Microbiota and Fermentation Characteristics

“…Reducing methane (CH 4 ) emissions from anthropogenic activities is of considerable interest since enteric fermentation from ruminants accounts for 25% of the 40% derived from agriculture (Olivier et al, 1999; Steinfeld et al, 2006). Ruminants are considered economically important due to their capacity to digest low-quality forages (Flint, 1997) and their ability to convert these substrates into energy is largely dependent on the rumen microbiota (i.e., bacteria, anaerobic fungi, protozoa, and methanogenic archaea) which converts indigestible plant material into usable energy for the host.…”

Development of Multiwell-Plate Methods Using Pure Cultures of Methanogens To Identify New Inhibitors for Suppressing Ruminant Methane Emissions

“…Methanomassiliicoccaceae-affiliated species are also found (4). A number of technologies have been suggested for mitigating methane emissions (5,6), including lowmethane-emitting animals (7) and the use of special forages (8), phage or their lytic enzymes (5,9), direct-fed microbials (10), vaccines (11), and inhibitors (12)(13)(14)(15). Although some of these strategies have shown promise, not all directly target methanogens.…”