Physiology of Digestion in the Macropodine Marsupials

Abstract

The macropodines (kangaroos and wallabies) are herbivorous marsupials with a digestive system comparable to the ruminants. Ingested food is subjected to extensive microbial fermentation and modification in a capacious forestomach and secondary fermentation occurs in the caecum-proximal colon. The macropodine stomach is essentially a long tubular structure, markedly different to that of the ruminants, and relationships between stomach structure and digesta flow have not been previously investigated. Similarly, little is known of the mode of microbial activity in the forestomach and quantitative estimates of the extent of microbial fermentation have not been reported. The present comparative study was undertaken to examine some of these aspects of the physiology of fermentative digestion in three macropodine species; 'Thylogale thetis' (red-necked pademelon), 'Macropus giganteus' (eastern grey kangaroo) and 'Macropus eugenii' (tammar wallaby). These species represent adaptation to widely different habitats. Reference was also made to other macropodine species and some direct comparisons were made with sheep.