Reprod. Nutr. Dev. 43 (2003) 41-55
DOI: 10.1051/rnd:2003005

Effect of coconut oil and defaunation treatment on methanogenesis in sheep

Andrea Machmüller, Carla R. Soliva and Michael Kreuzer

Institute of Animal Science, Animal Nutrition, Swiss Federal Institute of Technology (ETH), ETH Zentrum/LFW, CH-8092 Zurich, Switzerland
(Received 21 May 2002; accepted 12 December 2002)

Abstract
The present study was conducted to evaluate in vivo the role of rumen ciliate protozoa with respect to the methane-suppressing effect of coconut oil. Three sheep were subjected to a 2 2 factorial design comprising two types of dietary lipids (50 g kg ^-1 coconut oil vs. 50 g kg ^-1 rumen-protected fat) and defaunation treatment (with vs. without). Due to the defaunation treatment, which reduced the rumen ciliate protozoa population by 94% on average, total tract fibre degradation was reduced but not the methane production. Feeding coconut oil significantly reduced daily methane release without negatively affecting the total tract nutrient digestion. Compared with the rumen-protected fat diet, coconut oil did not alter the energy retention of the animals. There was no interaction between coconut oil feeding and defaunation treatment in methane production. An interaction occurred in the concentration of methanogens in the rumen fluid, with the significantly highest values occurring when the animals received the coconut oil diet and were subjected to the defaunation treatment. Possible explanations for the apparent inconsistency between the amount of methane produced and the concentration of methane-producing microbes are discussed. Generally, the present data illustrate that a depression of the concentration of ciliate protozoa or methanogens in rumen fluid cannot be used as a reliable indicator for the success of a strategy to mitigate methane emission in vivo. The methane-suppressing effect of coconut oil seems to be mediated through a changed metabolic activity and/or composition of the rumen methanogenic population.

Key words: lipid / nonyl phenol ethoxylate / Archaea / ciliate protozoa / ruminant

Correspondence and reprints: Andrea Machmüller
    e-mail: andrea.machmueller@inw.agrl.ethz.ch

© INRA, EDP Sciences 2003