SUCROSE INTOLERANCE IN BIRDS - SIMPLE NONLETHAL DIAGNOSTIC METHODS AND CONSEQUENCES FOR ASSIMILATION OF COMPLEX CARBOHYDRATES

Gray Catbirds (Dumetella carolinensis, Mimidae) and Purple-headed Glos sy-Starlings (Lamprotornis purpureiceps, Sturnidae) showed depressed i ngestion and increased fecal sugar contents when shifted from glucose and fructose to sucrose solutions. These species also exhibited no inc reases in plasma glucose after ingestion of sucrose, but an increase i n plasma glucose after ingestion of equicaloric doses of a mixture of glucose and fructose. In vitro measurements of intestinal disaccharida se activities in D. carolinensis revealed insignificant sucrase activi ty, and low levels of maltase activities. These results support the hy pothesis that sucrose intolerance is a shared-derived character of the monophyletic lineage that includes starlings, mimids, and thrushes, a nd indicate that sucrose intolerance in birds can be easily diagnosed with a combination of behavioral and nonlethal physiological measureme nts. We suggest that, in birds, low intestinal maltase activity is cor related with the lack of sucrase activity. We further hypothesize that sucrose-intolerant birds are poor at assimilating complex carbohydrat es.