Climate Change Metagenomic Record Index

MGnify Record MGYS00000566

Description
Manipulation of the rumen microbial ecosystem to increase the efficiency of nutrient use by the animal, or to decrease its environmental impact, has long been a goal for nutritionists and gut microbiologist. This paper investigates the effect and mode of action of chitosan (CHI) and ivy fruit saponins (IVY) when used as novel feed additives for ruminants. These compounds were supplemented at 5% inclusion rate into a control diet (CON) in a rumen simulation technique. Both, CHI and IVY had a strong and similar ability to decrease methane emissions in comparison to CON (-42% and -40%, respectively). The mode of action of these feed avidities was however remarkably different: CHI promoted a shift in the fermentation pattern towards more energetically favourable pathways (propionate) which explained about two thirds of the decrease in rumen methanogenesis. This shift was achieved by a simplification and modification of the structure in the bacterial community consisting on an increment of Bacteroidetes and Proteobacteria in detriment of Firmicutes and Fibrobacteres. This substitution of fibrolytic bacteria by amylolitic bacteria induced by CHI resulted on a 2.5-fold increase in the amylase enzymatic activity, lactate concentration (+53%) and microbial protein yield (+14%) with no detrimental effect on feed digestibility. Additionally, CHI decreased the relative abundance of methanogens respect to total bacteria which could also contribute to lower rumen methanogenesis. On the contrary, IVY promoted only minor changes on the fermentation pattern and on the structure of the bacterial community which explained only one third of the observed decrease in rumen methanogenesis. Instead, IVY had a specific effect on the methanogens population. This effect consisted on a change in the structure of the methanogens community and a decrease in its diversity. This specific effect, together with the anti-protozoal activity, can be thus considered the main anti-methanogenic property for IVY. Moreover IVY showed to have some beneficial effect to buffer the post-prandial drop in rumen pH and to decrease rumen ammonia levels (-61%), but its anti-microbial properties had a negative impact on microbial protein synthesis (-10%). Therefore, both CHI and IVY should be further investigated in vivo in order to determine the optimum doses which maintain low rumen methanogenesis but prevent negative effects on the rumen microbial ecosystem.