Methane production and digestibility measurements in the grey kangaroo and sheep

Three grey knagaroos and three sheep were given a diet of lucerne chaff and measurements were made of feed intake, digestibility coefficients, methane production rate and volatile fatty acid content of the "stomach" and caecum for each animal. The kangaroos had lower intakes of digestible dry matter and organic matter than the sheep; this was related to lower intakes of dry matter and lower apparent digestibility coefficients particularly of the crude fibre fraction. Methane production in the sheep (collected in respired air through a mask) was 0-81 litre/h; no methane was collected in the respired air from kangaroos. Anal release of methane in sheep and kangaroos indicated that some methane was produced in the hind gut of kangaroos and that all of this methane was lost via the anus. This finding was different to the sheep which apparently excreted 80-90% of the hind gut methane via the lungs. Thus in both sites of apparent high microbial growth in the gut of kangaroos methane production is negligible or lower than in the same sites in sheep. Possible explanations for the absence of measurable methane production in the kangaroo fore-stomachs are discussed.