Total Amino Acid Release Rates of Soluble and Insoluble Protein Fractions of Concentrate Feedstuffs by Streptomyces griseus

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Abstract
S. griseus (5 mg) protease was incubated with increasing protein concentrations of casein, soybean meal or corn gluten meal. Rates of amino acid release were 1.04, 0.72, and 0.36 .mu.mol of amino acid/h with enzyme saturation at 7.5 and 8.5 mg of casein and soybean meal protein. A ratio of protein to enzyme of 1.25 gave rates of release within saturation limits for protein sources differing in degradability. Partitioning of N fractions for 11 protein and 6 energy concentrate ingredients showed dehydrated alfalfa and corn gluten feed had largest proportions of soluble N, and amino acids, and least amount of potentially available insoluble protein compared to other protein ingredients. Incubation of S. griseus protease with soluble and insoluble protein fractions indicated that most feedstuff soluble protein fractions have amino acid release rates 2-3 times faster than insoluble protein fractions. Ratio of soluble to insoluble protein amino acid release were 1.2 for corn gluten meal and peanut meal, and 0.5 for dehydrated alfalfa and corn gluten feed. Soluble protein fractions of certain protein feedstuffs may not be as available in the rumen as insoluble protein fractions.