A Comparison of Four Methods for Determining Available Lysine in Animal Protein Meals

The available lysine in 7 fish, 10 meat and bone, and 6 keratin meals was determined with 2,4,6-trinitrobenzene sulfonic acid (TNBS) and 1-fluoro-2,4-dinitrobenzene (FDNB) chemical procedures, chick bioassay (CBA), and digestible lysine (DL) technique. The percent available lysine and total lysine (TL) in test meals is reported as grams of lysine per 100 g dry weight. The available lysine means determined by the TNBS, FDNB, CBA, and DL procedures were 5.28, 4.34, 4.50, and 4.36% for fish meals; 2.48, 2.53, 2.71, and 2.61% for meat and bone meals; and 2.33, 2.74, 1.50 and 1.92% for keratin meals, respectively. The correlation coefficients (r) for CBA versus TNBS lysine, FDNB lysine, DL, and TL are .90, .83, .97, and .93, respectively, for all animal proteins tested. The available lysine determined by the DL procedure correlated best with available lysine determined with the CBA for each type of animal protein meal and for all test meals collectively. The DL technique is a logical alternative to the CBA, FDNB, and TNBS procedure for determining available lysine in animal proteins because the DL procedure is simpler, less expensive, and quicker than the CBA procedure and more accurate than the colorimetric chemical procedures.