Age-Specific Changes in the Major Body Components and Caloric Value of Growing Japanese Quail

Abstract

BIOENERGETIC studies of birds have often been hampered by a lack of accurate caloric conversion factors for the live-weight biomass of the species being studied. This has been particularly true in studies of the energy-conversion efficiencies of growing nestlings, whose biomass may show significant changes in caloric value with increasing age (Ricklefs 1967a, Brisbin 1969). It is also possible that the pattern of such agespecific changes might differ between species showing altricial and precocial growth patterns. Although several altricial species have been studied in this regard (Brenner 1964, Ricklefs 1967a, Brisbin 1969, Myrcha and Pinowski 1970), very few comparable data are available for the more economically important precocial species, especially those within the order Galliformes. Biomass analyses of gallinaceous birds are often complicated by the fact that these species usually have large body sizes, requiring extensive homogenization and subsampling to estimate accurately their composition and caloric value (Brisbin 1968). A combination of small body size and rapid attainment of adult weight makes the Japanese Quail (Coturnix coturnix japonica) an ideal subject for studying growthrelated changes in the major body components and caloric values of a precocial gallinaceous species. To make the results of this study directly comparable with those of other species, changes in biomass composition and caloric density are expressed as functions of increasing age. Age, in turn, is expressed as percent of the total growing period. Although the Japanese Quail has been the subject of numerous growth analyses (Ernst and Coleman 1964, Collins and Abplanalp 1968, Marks and Lepore 1968, Woodard et al. 1969), none of these studies provides data that will allow the accurate calculation of the time required for this species to attain asymptotic weight under the conditions of this stucly. Therefore we used a refinement of the procedure described by Ricklefs (1967b) to analyze the growth of the birds.