It's in every newborn's job description: eat lots and grow fast. In their early days, freshly hatched house sparrows dine on a high protein diet of insects before their parents begin delivering starchy seeds to their voracious offspring. Pawel Brzęk and his colleagues from the University of Wisconsin and Universidad Nacional de San Luis wondered how the youngsters'digestive tracts respond to the drastic diet change while working full-out to keep pace with the youngsters' growth().
Feeding young sparrows on either a high-protein starch-free diet or a diet supplemented with starch, the team tracked the youngsters' growth, digestive tract enzyme levels and their ability to maintain their own body temperature until the birds were close to fledging.
The team found that although the birds on a starch-free diet were slightly smaller and took a little longer to maintain their own temperature, removing starch from the diet didn't seem to compromise the youngsters' growth. And when they checked the birds' intestines, the team also found that the levels of a carbohydrate-digesting enzyme, maltase, doubled when the birds were on a starchy diet; their intestines were definitely responding. Brzęk and his colleagues suspect that the hatchlings' maltase increase is `important for maintaining digestive efficiency and rate at the whole animal level,' allowing the youngster to process the enormous amounts of starch they consume. They believe that although some of the changes in the youngsters' intestines are`hard wired' by a genetic programme, others are governed by the diet change itself.
