Abstract
A total of 360 broiler chickens (25-day-old) allocated into 2 rooms, were inoculated with Escherichia coli (0 group-78) isolated from a case of colibacillosis in poultry through aerosol, on the 4th day after NB live vaccine administration. This strain was relatively insensitive or resistant to various antibiotics (doxycycline). The chickens in each room were divided into 2 groups, medicated with doxycycline, Vibra Vet, (24 mg per kg of body weight with drinking water at 27 or at 27 and 29-day-old) and non-medicated groups.
The death rate due to coli septicemia in the medicated groups was less than that in non-medicated groups. After 21 days of isolation the medicated group showed a lower mortality rate, better weight gain and feed efficiency in comparison with the non-medicated group in both rooms.
