In vitro screening of natural feed additives from crustaceans, diatoms, seaweeds and plant extracts to manipulate rumen fermentation

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), Ascophyllumnodosum (ASC), Laminariadigitata (LAM), neemoil (NOIL) and an ivy fruit extract rich in saponins (IVY). Dose-response incubationswere conducted to determine their effect on rumenfermentation pattern and gas production, while their anti-protozoal activity was tested using C-14-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 frombutyrate 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 fromacetate 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 rumenmicrobial ecosystem. (C) 2015 Society of Chemical Industry