Reductive Acetogenesis in the Hindgut and Attempts to its Induction in the Rumen—A Review

Abstract

Fievez, V., Piattoni, F., Mbanzamihigo, L. and Demeyer, D. 1999. Reductive acetogenesis in the hindgut and attempts to its induction in the rumen—A review. J. Appl. Anim. Res., 16: 1–22. Hindgut fermentation differs from rumen fermentation by a lower methane production and the presence of reductive acetogenesis (RA). Moreover, it has been shown that with ageing RA is replaced completely (rumen) or partially (hindgut) by methanogenesis (M). In some animals, as well as in humans, the importance of M has been related to a genetic predisposition, although from results obtained with rabbit caecal contents, this remains questionable. Former results suggested the importance of easily fermentable substrate for RA, more specific recent data suggest a promoting effect for homoacetogenic growth. In a second part of the paper attempts to induce RA in the rumen are reviewed. Neither addition of free amino acids, mucins, hydrogenotrophic substrates or bile salts were able to stimulate RA during batch incubations with rumen contents, even after selective inhibition of M. Only the introduction of a reductive strain Peptostreptococcus productus after selective inhibition of M by 2-BES or addition of a bacteriocin like inhibitor of M (Lactobacillus plantarun 80), resulted in induction of RA in short and long term in vitro incubations with rumen contents. However, in vivo reduction of M in the sheep rumen was not accompanied by RA and methane production recovered after a short period.