Studies on the Nutrition of Macropodine Marsupials. 2. Urea and Water Metabolism in Thylogale Thetis and Macropus Eugenii; Two Wallabies From Divergent Habitats.

Abstract

Urea and water metabolism were studied in the red-necked pademelon Thylogale thetis. and tammar wallaby Mucropus eugenii fed diets of chopped lucerne hay and fresh grass Phalaris aquatica ad libitum. On both diets T. thetis consumed more nitrogen (P<0.05), plasma urea levels were higher (P<0.05) and urea entry rate was greater (P<0.05) than in M. eugenii. Urea excretion rate was greater (P<0.05) in T. thetis than in M. eugenii on the lucerne diet, and urea degradation rate was greater (P<0.05) in T. thetis on the Phalaris diet. The proportion of urea synthesized that was recycled to and degraded in the digestive tract was similar (52-56%) in both species on both diets. T. thetis consumed more water (feed and drinking water) (P<0.05), and water turnover time was less (P<0.05) and turnover rate greater (P<0.05) than in M. eugenii, on both diets. At least on diets of adequate nitrogen and digestible energy content, it appears that differences in nitrogen metabolism between T. thetis and M. eugenii are not attributable to differences in gut microbial activity; rather, the results of this and other studies suggest that M. eugenii has a greater urine-concentrating ability and lower maintenance requirements than T. thetis.