Clinical evaluation of prophylactic regimens for bovine respiratory disease

Abstract

Experiments were conducted using a 3 by 2 factorial design to evaluate the efficacy of Haemophilus somnus and unspecified Pasteurella inactivated vaccines and to compare the oral and intramuscular route of administration of a BVD vaccine. 303 crossbred steer calves with an average weight of 222 kg were purchased and any animal showing clinical signs of illness excluded. All calves in the trial received an intranasal IBR vaccine, 2.5 million units of vitamin A intramuscularly, three 36 mg implants of zeranol, multivalent clostridial vaccine and levamisole. Calves were randomly assigned to treatment groups by a random number table. 45 randomly-selected calves distributed among all treatment groups were bled during processing and again 42 days after vaccination to collect paired samples. The calves were checked daily and any with clinical signs of respiratory disease were treated. The calves were weighed on arrival and at 34, 72 and 106 days, and daily feed consumption was calculated. The pasteurella vaccine reduced the incidence of BRD and improved the response to treatment. The result disagrees with previous findings, perhaps because of differences in prior exposure, movements in marketing channels or the virulence of the bacteria. The BRD morbidity rate and response to treatment were no different for the oral and intramuscular route of administration. However, the immune response to the BVD vaccine as measured by serum neutralisation was greater following oral administration.