Lime treatment of keratinous materials for the generation of highly digestible animal feed: 2. Animal hair

Air-dried cow hair was treated using Ca(OH)(2) (insoluble in water but dissolved during reaction) at 100 degrees C. To obtain a liquid product rich in amino acids, a well-insulated, stirred reactor was used to perform the hydrolysis process for different time periods. High lime loadings and a long treatment period convert 70% of cow hair to soluble amino acids and polypeptides. Protein solubilization varies with lime loading especially for the long-term treatment (t > 12 h) showing that the hydroxyl group is required as a catalyst for the hydrolysis reaction and that lime is consumed during the process; as a consequence lower lime loading generate lower conversions. A very perceptible ammonia odor in the soluble product suggests amino acid degradation. Arginine, threonine, and serine are the more susceptible amino acids under alkaline hydrolysis. The amino acid composition of the solubilized product compares poorly with the essential amino acid requirements for various monogastric domestic animals, but it has value as ruminant feed. (c) 2005 Elsevier Ltd. All rights reserved.