Nutritive value of protein in high and low protein content sorghum grain as measured by rat performance and amino acid assays.

The nutritive value of protein of 2 sorghum grain composites containing 7.9% and 11.8% protein, respectively, was compared on the basis of growth of rats and amino acid analyses. The high protein sorghum grain had higher percentages of all the 17 amino acids studied than did the low protein sorghum grain. In both grains, lysine was the most deficient amino acid, and content of sulfur-containing amino acids and threonine also was low. Calculated on an equal nitrogen basis, the dibasic amino acids, especially lysine, the sulfur-containing amino acids, and threonine levels of the high protein sorghum grain were lower than those of the low protein sorghum grain. Nutri tive value of the protein of low protein sorghum grain was superior to that of a high protein sorghum grain, as shown both by growth of rats and amino acid assays. When lysine, histidine, and arginine were added to the high protein sorghum grain diet to adjust percentages of those amino acids in the protein similar to the content in the low protein sorghum grain diet, an increase in growth resulted. Sorghum grains are used widely in feeds for poultry, swine and other farm animals. Factors such as environment and hybrids are known to cause variations in protein content of sorghum grains (1). With the expanding use of irrigation, fertilization, and hybrid seed in farming practices, the protein content of sorghum grain may vary more than formerly. There is a paucity of information on the effects of variation in protein content on the nutritive value of protein from sorghum grain. However, the nutritive value of corn has been studied more extensively. Sauberlich et al. (2) determined protein and 18 amino acids in a series of corn samples. Both variety and nitrogen fertilization influenced protein and amino acid content, but in the higher protein content corn, leucine, alanine, phenylalanine and proline made up a greater percentage of the protein than the others, whereas, arginine, glycine, lysine and tryptophan became a lesser percentage of the protein. Sauberlich et al.2 stated that the main effect of nitrogen fertilization of corn was on quantity of protein rather than quality. Using rats and chicks as test animals, Sauberlich et al. (3) determined the nutri tive value of corns ranging from 6.8 to 13.6% protein. High protein corn was superior to low protein corn when fed as equal proportions of grain in the diet. For growth of their animals, both high and low protein corn were deficient in tryptophan and lysine, and the low protein corn was deficient also in isoleucine, threonine, and valine. When corn was fed on the basis of equal protein content in the diet, high protein corn was somewhat inferior to low protein corn. Vavich et al. (4) observed that, as meas ured by chick growth, sorghum grain con taining 10.5% protein was superior to sorghum grain containing 15.3% protein when fed at a constant level of protein in the diet. Using microbiological amino acid assays they found that the diet made with the 10.5% protein sorghum grain was low in lysine and arginine, and that made with the 15.3% protein sample was high in leucine and isoleucine. The object of the present experiment was to determine the nutritive value of protein of high and low protein hybrid Received for publication October 25, 1965. 1 Contribution no. 522, Department of Flour and Feed Milling Industries, and no. 60, Department of Biochemistry, Kansas Agricultural Experiment Station, Manhattan, Kansas. 2 Sauberlich, H. E., W-Y. Chang and W. D. Salmon 1951 Effect of nitiDgen fertilization upon the bio logical value and amino acid content of corn. Federa tion Proc., 10: 243 (abstract). 370 J. NUTRITION, 88: '66 at India: A S N A S posored on M arch 2, 2012 jn.nition.org D ow nladed fom NUTRITIVE VALUE OF PROTEIN IN SORGHUM GRAINS 371 sorghum grain, as measured by growth of rats, and to correlate these data with the amino acid content of the protein.