CHANGING THE CHICK'S REQUIREMENT OF ARGININE BY SELECTION

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Abstract
By selection and testing during a period of 4 1/2 years, 2 lines of White Leghorns were bred which differed widely in their requirement of arginine. Chicks were tested for their ability to survive and grow for 4 weeks after hatching on a synthetic diet deficient in arginine. Selection was based on evaluation of families and the use of proven sires and dams for annual reproduction of the 2 lines. Some birds that had themselves survived the tests were also used as breeding stock to produce the 4th selected generation. In tests of that 4th generation on the deficient diet, among 277 chicks of the high-requirement line, mortality was 27.8%, average weight of survivors 110.5 g, and these survivors attained only 36.4% of the average weight of controls. In concurrent tests of the low-requirement line, mortality was only 1.8%, and average weight of survivors was 258.4 g, which was 82.3% of the weight of controls. The 2 strains did not differ significantly in other measures of biological efficiency. The significance of these results is briefly discussed.