Does shifting from a commercial to a natural diet affect the nutritional status of hand-reared grey partridges Perdix perdix?

Two feeding trials on hand-reared grey partridges Perdix perdix were perfor med to study the effect of a change from a commercial to a natural diet on body mass, food consumption, metabolised energy coefficient, gut morphology and some blood metabolites. We simulated the abrupt change in the diet whi ch takes place when hand-reared birds are released into the wild, in the te st group body mass decreased significantly after the change in diet. Howeve r, within one week body mass started to increase again, but it stabilised a t a lower level than in control birds. Birds in the test group consumed mor e food (fresh weight) during the feeding trial and even produced more excre ta during the second, fourth and fifth week of the feeding trial. Gross ene rgy intake, amount of metabolised energy and metabolised energy coefficient decreased and excretory energy content increased during the feeding trial. No differences were seen in the analysed blood metabolites. Gizzards of th e test birds were heavier than gizzards of the control birds. We conclude t hat the abrupt change from a commercial to a natural diet with the followin g difference in diet composition affects the partridge's ability to utilise nutrients from food available in the wild. According to our study, a perio d of six weeks may be inadequate for partridges to get totally adapted to a new diet.