Microbial Activity in the Forestomach of Free-Living Macropodid Marsupials - Comparisons With Laboratory Studies

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Abstract
Parameters of fermentative digestion were measured in five species of macropodid marsupials shot while feeding in the wild. These included details of microbiota, fermentation products (volatile fatty acids, gas, ammonia) and forestomach digesta pH. Ciliate protozoa and fungi, similar to anaerobic rumen fungi, were present in the forestomach of all species except Thylogale thetis. The bacterial flora was complex and numbers were similar to those in the ruminant forestomach. The forestomach gas contained more methane than found previously in captive macropodids, and in Wallabia bicolor hydrogen was present at 10- 11% of total gas. The pH of forestomach digesta was 5.7-6.7, indicative of animals actively feeding. Comparisons of stomach fill, ammonia and volatile fatty acid (VFA) concentrations and molar proportions, and rates of VFA production in the forestomach and hindgut, indicated that conclusions on digestive function in macropodids derived from studies on captive animals are generally applicable to free-living macropodids. The main differences probably lie in greater levels of feed intake in the field, and in greater opportunity for free-living macropodids to select from a more heterogeneous diet.