The Amino Acid Deficiencies of Gelatin for the Growing Chicken

EARLY attempts by Jackson et al. (1928) and Kruse et al. (1934) to promote optimal growth in rats fed gelatin-containing diets supplemented with the amino acids then known (1928–34) to be deficient failed. At that time, however, threonine had not been identified as an essential amino acid. Even in the light of newer knowledge a decade later, Hier et al. (1944) were still unsuccessful in obtaining good growth in rats fed amino acid-supplemented gelatin diets. These workers reported slower growth on the amino acid-supplemented gelatin diets than for the amino acids fed separately. They concluded that the difficulty with gelatin might be due to an inhibitory effect caused by the unusually high content of glycine and proline. Fourteen years later Summers and Fisher (1962) again tried, unsuccessfully, to simulate the amino acid pattern and the growth response of isolated soy-protein in chicks fed amino acid-supplemented gelatin diets. In these …