“…Borrowing the adult macronutrient-selection procedure, our laboratory obtained evidence that growing chicks, like adults, could construct a nutritionally adequate diet from individual dietary components (Hayne, Rovee-Collier, & Gargano, 1986;Kaufman, Collier, & Squibb, 1978;Rovee-Collier, Clapp, & Collier, 1982). In the initial study using this paradigm, for example, we offered 10-dayold chicks a simultaneous choice between separate sources of different fractions of macronutrients (protein and carbohydrate) and found that chicks could select a protein-carbohydrate ratio that supported growth at the rate of nonselecting controls (Kaufman et al 1978). In subsequent studies, we found that even younger chicks could systematically alter their relative intakes of the same protein and carbohydrate fractions in a way that yielded optimal growth in different ambient temperatures (Hayne et al, 1986;Rovee-Collier, Collier, Egert, & Jackson, 1993) and when the protein and carbohydrate fractions were successively accessible only at certain portions of the photoperiod (Rovee- Collier et al, 1982).…”