THE NUTRITIONAL VALUE OF INCREASED LEVELS OF PROTEIN RESULTING FROM NITROGEN FERTILIZATION OF BARLEY

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Abstract
Samples of barley having low, medium, and high protein contents were obtained from field fertilizer experiments conducted during 1957 and 1958. The nutritive values of these grains were compared in a feeding trial employing rats as the test animal, and by a semi-quantitative chromatographic estimation of 13 amino acids in the grains. For the feeding experiment all diets were supplemented with minerals and vitamins. Each grain sample was fed with and without added lysine. Animal growth and food efficiency improved with increase in protein levels and with addition of lysine. The 13 amino acids determined accounted for approximately two-thirds and four-fifths of the total protein in the 1957 and 1958 grains respectively. Possible causes of these differences are discussed. The analytical data revealed that percentages of 9 essential amino acids in barley protein were approximately double the amounts reported by other analytical procedures. Compared to previously reported data, there were some noteworthy variations for individual amino acids. There may be practical applications of the procedure used for amino acid determinations in evaluating the protein quality of feed grains. The availability of such a technique could be very helpful to plant breeders concerned with the production of feed grain varieties. The feeding experiment established the nutritive importance for rats, and presumably for swine, of grain protein increases resulting from nitrogen fertilization.