Methane production by red-necked wallabies (Macropus rufogriseus)

Abstract

The claimed low production of CH4 by kangaroos and marsupials in general has been questioned because of a lack of data. The extent of their CH4 production is of interest both from the point of view of discussing meat production of marsupials and as a basis for developing methods to reduce CH4 production from ruminants. In the present experiment, the CH4 production of 8 red-necked wallabies (Macropus rufogriseus) was measured of which 4 were fed 2 different diets in an open-circuit respiration chamber. These results were compared with a newly developed, inexpensive, and simple method that does not influence the behavior of the animal, and where the ratio between CH4 and CO2 is measured and used together with the calculated CO2 to quantify the CH4 production. The experiment demonstrated that the wallabies produce CH4. However, the amount of CH4 produced by these wallabies was between 1.6 and 2.5 L/d equivalent to 1.6 and 2.5% of GE or 2.2% and 3.5% of DE intake and 0.22 L/BW, kg0.75. This is between 25 and 33% of what can be expected from ruminants fed the same diet. Based on the uneven release of CH4 with time, it is most likely that the CH4 is excreted through flatulence and not through breathing as is seen in ruminants. The experiments also showed that a reasonably accurate determination of the CH4 production of a group of animals can be obtained by simply measuring the CH4/ CO2 ratio over a limited time span. This may represent the situation in a natural setting better than measurements in a respiration chamber. It was found that the CH4/CO2 ratio in itself represents a reasonable prediction of the proportion of feed GE that is lost as CH4, and that this method offers new opportunities for CH4 measurements on a large number of animals. © 2012 American Society of Animal Science. All rights reserved.