Dietary supplemental plant oils reduce methanogenesis from anaerobic microbial fermentation in the rumen

Abstract

Ruminants contribute to the emissions of greenhouse gases, in particular methane, due to the microbial anaerobic fermentation of feed in the rumen. The rumen simulation technique was used to investigate the effects of the addition of different supplemental plant oils to a high concentrate diet on ruminal fermentation and microbial community composition. The control (CTR) diet was a high-concentrate total mixed ration with no supplemental oil. The other experimental diets were supplemented with olive (OLV), sunflower (SFL) or linseed (LNS) oils at 6%. Rumen digesta was used to inoculate the fermenters, and four fermentation units were used per treatment. Fermentation end-products, extent of feed degradation and composition of the microbial community (qPCR) in digesta were determined. Compared with the CTR diet, the addition of plant oils had no significant (P > 0.05) effect on ruminal pH, substrate degradation, total volatile fatty acids or microbial protein synthesis. Gas production from the fermentation of starch or cellulose were decreased by oil supplementation. Methane production was reduced by 21-28% (P < 0.001), propionate production was increased (P < 0.01), and butyrate and ammonia outputs and the acetate to propionate ratio were decreased (P < 0.001) with oilsupplemented diets. Addition of 6% OLV and LNS reduced (P < 0.05) copy numbers of total bacteria relative to the control. In conclusion, the supplementation of ruminant diets with plant oils, in particular from sunflower or linseed, causes some favorable effects on the fermentation processes. The addition of vegetable oils to ruminant mixed rations will reduce methane production increasing the formation of propionic acid without affecting the digestion of feed in the rumen. Adding vegetable fats to ruminant diets seems to be a suitable approach to decrease methane emissions, a relevant cleaner effect that may contribute to alleviate the environmental impact of ruminant production. Ruminant herbivory is characterized by foregut microbial anaerobic fermentation of structural carbohydrates from fibrous plant-based feedstuffs providing nutrients for the animal 1. Moreover, ruminal microbes break down all components of the diet, with characteristic pathways involved in the degradation of fiber and non-structural carbohydrates, proteins and lipids 2,3. Ruminal fermentation can be considered beneficial in many aspects, but has also impacts on the environment. One of the global environmental impacts of livestock agriculture is the release of greenhouse gases (GHG) into the atmosphere 4,5 , in particular methane, a gas responsible for 20% of the global warming produced by all GHG 6,7. It is estimated that raising farm animals accounts for about 16% of anthropogenic GHG emissions, with two-thirds of the total livestock GHG emissions produced by ruminants. Methane (CH 4

Review: Strategies for enteric methane mitigation in cattle fed tropical forages

“…Feeding sunflower oil can effectively reduce enteric methane emissions of dairy cows (Bayat et al, 2017). Similar effects of vegetable oils on reducing methane emissions have been reported under in vitro conditions (Vargas et al, 2020). Recent work carried out at the University of Yucatan, Mexico (Flores-Santiago, E. unpublished results), has shown that by feeding palm oil (6% of ration DM) to hair Pelibuey sheep housed in respiration chambers, which were fed a low-quality basal ration of tropical C4 grass (Brachiaria brizantha) hay, methane yield was reduced by~14%, compared to a control treatment without palm oil.…”

Targeted and Untargeted Metabolic Profiling to Discover Bioactive Compounds in Seaweeds and Hemp Using Gas and Liquid Chromatography-Mass Spectrometry

“…In general, the lipid content of seaweeds is low, varying between 1% and 5% DM [ 7 ], but there are substantial differences between the species when studying the elution profiles using untargeted LC-MS. Hemp leaves and stems, on the other hand, have higher lipid contents, of 19.97% and 8%, respectively [ 39 ]. Studies with ruminants have shown that PUFAs in the diet can reduce methane emissions by acting as hydrogen sinks because biohydrogenation of PUFAs can compete with methanogenesis for metabolic H 2 [ 40 ]. To our knowledge, no studies investigating glycolipids and methane reduction have been undertaken.…”

Phytogenic Additives Can Modulate Rumen Microbiome to Mediate Fermentation Kinetics and Methanogenesis Through Exploiting Diet–Microbe Interaction

“…Variable effects of vegetable oils and unsaturated FA on CH 4 emission might be associated with the double bond number per FA, type of oil (free oil or whole seed), and composition (roughage-to-concentrate ratio) of the rations (134). An in vitro study of Vargas et al (141) shows that supplementation of vegetable oil (sunflower and linseed) at 6% in high-concentrate TMR has the potential to reduce CH 4 emission (up to 21-28%), butyrate concentration, and A:P, while increasing propionate concentration. Recently, a meta-analysis showed that addition of nitrates and vegetable oils in cattle diet has the ability to reduce CH 4 emission up to 6-20% (118).…”