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Tetracyclines having substantially no effective antibiotic or antibacterial activity and possessing anti-collagen-destructive enzyme activity or anti-collagenase activity and compositions containing the same have been found useful as anti-collagenolytic agents. Such tetracyclines and compositions containing the same are useful in the treatment of periodontal diseases, corneal ulcers, bone deficiency disorders, rheumatoid arthritis diseases characterized by excessive collagen destruction. A special aspect of this invention involves the incorporation of such tetracyclines in animal feed compositions for improved animal nutrition, such as may be evidenced by increased weight gain.