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In a herd of 70 bull calves (4-5 months of age) kept on pasture, 56 (80%) animals showed, after natural infection with Moraxella bovis (M. bovis), typical clinical signs of infectious bovine keratoconjunctivitis (IBK). Eyes with epiphora, photophobia, blepharospasm and/or a corneal ulcer with a diameter of less than 5 mm were considered as moderately affected. Those with a corneal ulcer > 5 mm diameter and/or even more profound findings were considered as severely affected. The objective was to study in IBK affected calves in a prospective randomized case control study the therapeutic efficacy of intrapalpebral (i.p.) injections of oxytetracycline (OTC) (200 mg OTC-hydrochloride 10% in the upper eyelid of moderately affected and in both eyelids of severely affected eyes) and intramuscular (i.m.) treatment (long-acting OTC-dihydrate; 20 mg/kg body weight for both moderately and severely affected patients). 29 animals (20 moderately affected, 9 severely affected) were treated i.p. and 27 animals (19 moderately, 8 severely affected) were treated i.m.. For fly control, deltamethrin was applied to all bulls at d 0. The OTC-treatment was repeated at intervals of 3 - 8 d until recovery. All animals recovered within 42 days. The mean number of treatments per animal and the interval between diagnosis and assessment of healing were not affected by the method of OTC administration; the latter averaged out at about 10 d for moderately affected and 17 d for severely affected eyes. Significantly less medication was required per animal for i.p. than for i.m. treatments (moderately affected: 281 vs. 2033 mg; severely affected: 1156 vs. 3982 mg). In conclusion, both methods of OTC administration were found to be similarly effective for the treatment of IBK in calves.