British Journal of Nutrition

Full Papers

Microbiology

Inclusion of glycerol in forage diets increases methane production in a rumen simulation technique system

Jorge Avila-Stagnoa1a2a3, Alexandre V. Chavesa1 c1, Gabriel O. Ribeiro Jra2a4, Emilio M. Ungerfelda5 and Tim A. McAllistera2

a1 Faculty of Veterinary Science, University of Sydney, Sydney, NSW 2006, Australia

a2 Lethbridge Research Centre, Agriculture and Agri-Food Canada, Lethbridge, Alberta, Canada T1J 4B1

a3 Facultad de Ciencias Veterinarias, Universidad de Concepción, Chillan, Chile

a4 Escola de Veterinaria, Universidade Federal de Minas Gerais, Belo Horizonte, MG 30123-970, Brazil

a5 Centro de Investigación y Desarrollo CIEN Austral CONICYT Regional R10C1002, Puerto Montt, Chile

Abstract

We hypothesised that the inclusion of glycerol in the forage diets of ruminants would increase the proportion of propionate produced and thereby decrease in vitro CH4 production. This hypothesis was examined in the present study using a semi-continuous fermentation system (rumen simulation technique) fed a brome hay (8·5 g) and maize silage (1·5 g) diet with increasing concentrations (0, 50, 100 and 150 g/kg DM) of glycerol substituted for maize silage. Glycerol linearly increased total volatile fatty acids production (P< 0·001). Acetate production was quadratically affected (P= 0·023) and propionate and butyrate production was linearly increased (P< 0·001). Glycerol linearly increased (P= 0·011) DM disappearance from hay and silage. Crude protein disappearance from hay was not affected (P= 0·789), but that from silage was linearly increased (P< 0·001) with increasing glycerol concentrations. Neutral-detergent fibre (P= 0·040) and acid-detergent fibre (P= 0·031) disappearance from hay and silage was linearly increased by glycerol. Total gas production tended to increase linearly (P= 0·061) and CH4 concentration in gas was linearly increased (P< 0·001) by glycerol, resulting in a linear increase (P< 0·001) in mg CH4/g DM digested. Our hypothesis was rejected as increasing concentrations of glycerol in a forage diet linearly increased CH4 production in semi-continuous fermenters, despite the increases in the concentrations of propionate. In conclusion, this apparent discrepancy is due to the more reduced state of glycerol when compared with carbohydrates, which implies that there is no net incorporation of electrons when glycerol is metabolised to propionate.

(Received March 15 2013)

(Revised August 28 2013)

(Accepted August 29 2013)

(Online publication October 07 2013)

Key Words:

  • In vitro techniques;
  • Biodiesel by-products;
  • Hydrogen sink;
  • Methane

Correspondence

c1 Corresponding author: A. V. Chaves, fax +61 2 9351 3957, email alex.chaves@sydney.edu.au

Footnotes

  Abbreviations: ADF, acid-detergent fibre; NDF, neutral-detergent fibre; RUSITEC, rumen simulation technique; VFA, volatile fatty acid

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