Search

BACKGROUND Eight natural products from animal, unicellular algae, brown seaweed and plant origins were chosen according to their theoretical antimicrobial activity: Diatomaceous earths ( DE), insoluble chitosan ( ICHI), soluble chitosan ( CHI), seaweed meal ( SWM), Ascophyllum nodosum ( ASC), Laminaria digitata ( LAM), neem oil ( NOIL) and an ivy fruit extract rich in saponins ( IVY). Dose-response incubations were conducted to determine their effect on rumen fermentation pattern and gas production, while their anti-protozoal activity was tested using 14C-labelled bacteria. RESULTS DE, SWM, NOIL and ICHI had very small effects on rumen function when used at inclusion rate up to 2 g L−1. ASC had anti-protozoal effects (up to −23%) promoting a decrease in gas production and methanogenesis (−15%). LAM increased VFA production (+7%) and shifted from butyrate to acetate. CHI also shifted fermentation towards propionate production and lower methane (−23%) and protozoal activity (−56%). IVY decreased protozoal activity (−39%) and ammonia concentration (−56%), as well as increased feed fermentation (+11% VFA concentration) and shifted from acetate to propionate production. CONCLUSIONS ASC, LAM, CHI and IVY showed promising potential in vitro as feed additives to improve rumen function , thus more research is needed to investigate their mode of action in the rumen microbial ecosystem. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

This study investigates the effects of supplementing a control diet (CON) with chitosan (CHI) or ivy fruit saponins (IVY) as natural feed additives. Both additives had similar abilities to decrease rumen methanogenesis (-42% and -40%, respectively) using different mechanisms: due to its antimicrobial and nutritional properties CHI promoted a shift in the fermentation pattern towards propionate production which explained about two thirds of the decrease in methanogenesis. This shift was achieved by a simplification of the structure in the bacterial community and a substitution of fibrolytic (Firmicutes and Fibrobacteres) by amylolytic bacteria (Bacteroidetes and Proteobacteria) which led to greater amylase activity, lactate and microbial protein yield with no detrimental effect on feed digestibility. Contrarily, IVY had negligible nutritional properties promoting minor changes in the fermentation pattern and on the bacterial community. Instead, IVY modified the structure of the methanogen community and decreased its diversity. This specific antimicrobial effect of IVY against methanogens was considered its main antimethanogenic mechanism. IVY had however a negative impact on microbial protein synthesis. Therefore, CHI and IVY should be further investigated in vivo to determine the optimum doses which maintain low methanogenesis but prevent negative effects on the rumen fermentation and animal metabolism. [ABSTRACT FROM AUTHOR]