Abstract

The aim of the present study was to compare in vitro methane (CH4) production and other fermentation parameters from different substrates incubated either in rumen or faecal inoculum. Five different substrates were incubated in two different inocula and gas recordings were made using an automated in vitro gas production system. The substrates were: particulate matter obtained from reticulo-rumen (RR) digesta and faeces (FC) by wet sieving, timothy hay (H), first cut grass silage (S) and a mixture of grass silage and barley (50:50; SB). One gram of each substrate was incubated either in 60 ml buffered rumen or faecal inoculum taken from Swedish lactating dairy cows for 48 h. The results indicated that in vitro total gas production, predicted in vivo CH4 production and the ratio of CH4 production to total gas production were greater (P < 0.01) for substrates incubated in rumen inoculum as compared to faecal inoculum. Mean of predicted in vivo CH4 production was greater for substrates incubated in rumen inoculum (23.5 ml/g DM, 29.0 mug OM) as compared to faecal inoculum (11.2 ml/g DM, 14.3 ml/g OM). Predicted CH4 production based on volatile fatty acids (VFA) stoichiometry equations (CH(4)VFA) showed no difference in CH4 per mol VFA (P=0.44) between the two sources of inoculum used for all substrates. Molar proportions of propionate were higher and that of butyrate were lower (P < 0.01) for all substrates incubated in faecal inoculum compared to rumen inoculum. No difference (P=0.13) in molar proportions of acetate was observed. Digestibility of neutral detergent fibre (aNDFomD) and true organic matter digestibility (TOMD) were lower (P < 0.01) for all substrates incubated in faecal inoculum compared to rumen inoculum. It can be concluded that using faecal inoculum tended to give lower values of predicted in vivo CH4 production as compared to rumen inoculum. The discrepancy between observed and stoichiometric CH4 production suggests an existence of acetogenesis in the hindgut. (C) 2015 Elsevier B.V. All rights reserved.

Keywords

Faeces; Hindgut fermentation; Methane; Ruminants; VFA

Published in

Livestock Science
2015, Volume: 181, pages: 65-71
Publisher: ELSEVIER SCIENCE BV

SLU Authors

• Ramin, Mohammad

  • Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences
    

• Huhtanen, Pekka

  • Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Animal and Dairy Science


Publication identifier

DOI: https://doi.org/10.1016/j.livsci.2015.09.025

Permanent link to this page (URI)

https://res.slu.se/id/publ/72235