Nutritional Responses of Pheasants to Corn, with Special Reference to High-Lysine Corn

IN LATE 1963, Purdue University scientists discovered, by amino acid analysis, that the endosperm of maize [Zea mays) kernels homozygous for the opaque-2 mutant contained about 70 percent more lysine than the endosperms of kernels of normal hybrids (Mertz et al. 1964: Mertz 1966:12). The endosperm of opaque-2 also contained greater amounts of tryptophan than that of normal corn ( Pickett 1966:19). Lysine and trytophan are among those amino acids that are dietary essentials for protein synthesis in many animals, including man. The proteins in endosperm of normal corn are of low biological quality. Thus the opaque-2 mutant, which alters the amino acid composition (particularly that of lysine, tryptophan, and leucine) of the maize endosperm, has offered the potential of a type of corn having exceptional nutritional values. The superior nutritional benefits of this modified-protein corn (hereinafter termed high-lysine corn) for growth have already been demonstrated in feeding experiments with rats (Mertz et al. 1965; Mcrtz 1966), swine (Pickett 1966: Jensen et al. 1967). chicks ( Rogler 1966 . and turkeys (.Adams & Rogler 1970). The nutritional potential of high-lysine corn has led to predictions that this corn may replace a substantial acreage of normal-corn hybrids produced in the Corn licit during the 1970"s. The estimated acreage of high-lysine corn planted in the United States in 1972 was 80,000-100,000 acres (D. E. Alexander. University of Illinois, personal communication, January 12, 1973). Inasmuch as corn is important in the diet of many wild animals, the widespread use of high-lysine corn offers a potential nutritional benefit to wild birds and mammals. Corn figures more prominently in the diet of midwestern pheasants, particularly in fall and winter, than it does for most wildlife species (Korschgen 1964: 170, 173). To illustrate, during fall and winter, corn constitutes at least 80 percent (by weight) of the total food intake by pheasants in thriving populations in east-central Illinois (Anderson & Stewart 1969:261; R. F. Labisky, unpublished data). Yet despite the importance of corn to pheasants, little is known of its nutritional attributes for growth, maintenance, or reproduction. Furthermore, juvenile hens, in contrast to adult hens, suffer a disproportionately high rate of nonhunting mortality between fall and winter in Illinois (R. F. Labisky, unpublished data) . That the onset of this mortality among juvenile hens coincides with that time of the year at which waste corn from the harvest suddenly becomes abundantly available suggests a potential causal link between unbalanced nutrition and mortality. Hence the objectives of this study were to ascertain the physiological responses of juvenile hen pheasants in fall, and of adult hen pheasants in late winter and early spring, to exclusive diets of both normal corn and high-lysine corn.published or submitted for publicationis peer reviewe