EFFECT OF GROWTH-RATE AND BODY-MASS ON RESTING METABOLIC-RATE IN GALLIFORM CHICKS

In this study, we asked whether within-species variation in chick rest ing metabolic rate was related to variation in growth and whether this relationship changed during development in three galliform species (t urkey, Meleagris gallopavo, guinea fowl, Numida meleagris, and Japanes e quail, Coturnix coturnix japonica). Resting metabolic rate increased by a bi- or triphasic pattern with body mass. For each phase, the rel ationship between metabolic rate and growth was studied by residual an alysis, with two measures of growth: growth rate and body mass. Chick mass reflects the net result of accumulated growth, while hatchling ma ss reflects embryonic growth. In hatchlings, high metabolic rates coin cided with low growth rates in turkeys and guinea fowl. These species delay initial food intake, and under these circumstances high metaboli c expenditure may preclude conversion of yolk energy into body mass. N o relationship was present between residual hatchling metabolic rate a nd residual body mass. In older chicks, residual metabolic rate was po sitively linearly related with residual growth rate (turkeys and young quail) or residual body mass (guinea fowl and older quail). The simil arity of the slopes suggests that growth rate and accumulated growth a ffected maintenance metabolism to the same extent throughout developme nt. These findings suggest that growth models must take ontogenetic ad justments of metabolic rate into account in addition to costs of maint enance.