The essential amino acid requirements for maintenance in the White-crowned Sparrow, Zonotrichia leucophrys gambelii

Abstract

An animal's nutritional status depends on (i) nutrient availability, (ii) its nutritional needs, and (iii) physiological, metabolic, morphological, and behavioral compensations that avert or minimize discrepancies, if any, between the first two factors. Of the factors determining nutritional status, the actual nutritional needs of wild animals have received the least attention by biologists. I report the requirements for each of the essential amino acids (EAAs) for maintenance of a small granivorous passerine, the White-crowned Sparrow (Zonotrichia leucophrys gambelii). I measured the maintenance requirements of wintering, adult sparrows under thermoneutral conditions, using synthetic diets that differed only in their concentrations of the EAA being investigated. I estimated EAA requirements on the basis of (i) changes in body mass, (ii) daily food intake, and (iii) N balance in birds fed different concentrations of the EAAs in diets containing 12% protein and 12.4 kJ apparent metabolizable energy per gram dry mass. For the most part, estimates of requirements based on these three indices were in agreement. The estimated requirements for the EAAs (mg/kJ basal energy expenditure), based on integrating the results from the above three indices, were as follows: Arg = 0.39, His = 0.11, Lys = 0.29, Ile = 0.27, Leu = 0.38, Val = 0.24, Met in the absence of Cys = 0.38, Phe in the absence of Tyr = 0.39, Thr = 0.19, and Tip ≤ 0.07. Cys and Tyr could supply about half of the above requirements for Met and Phe, respectively. Except for Lys and His, these requirements are consistent with those reported for adult domestic roosters.