ABSTRACT
A field trial compared a modified Pasteurella haemolytica biotype A serotype 1 leukotoxin vaccine to a commercial vaccine during March-July 1995 in a Natal Midlands, South African, feedlot. Weaners/long weaners purchased by the feedlot were allocated systematically into test vaccine and control vaccine groups of 1241 and 1240 head, respectively, and fed in groups of approximately 200 head. Morbidity and mortality were monitored until the animals were marketed. Details of pleuritis and pneumonia at veterinary meat inspection were recorded for 409 test-vaccinated and 424 control-vaccinated cattle. An increase in morbidity but not mortality risk of respiratory disease was shown between test (13.8% morbidity) and control (11.4% morbidity) groups. Cattle with a processing weight <245 kg were 1.4 times more likely to develop respiratory diseases than cattle with a processing weight > or =245 kg. Cattle bought on auction were 1.6 times more likely to develop respiratory disease than cattle bought at private sales. A partial farm budget incorporating Latin Hypercube sampling of uncertain variables was done to obtain the distribution of possible financial outcomes if the test vaccine were used. Impact (sensitivity) analyses indicated that median weight of carcass cut away had the greatest impact on the profit margin. The partial farm budget highlighted the importance of reducing sub-clinical lesions in a feedlot.
Subject(s)
Bacterial Vaccines , Cattle Diseases/economics , Cattle Diseases/prevention & control , Mannheimia haemolytica/immunology , Pasteurella Infections/veterinary , Respiratory Tract Diseases/veterinary , Animals , Cattle , Cost-Benefit Analysis , Pasteurella Infections/economics , Pasteurella Infections/prevention & control , Random Allocation , Respiratory Tract Diseases/economics , Respiratory Tract Diseases/prevention & control , Risk Factors , South Africa , Vaccination/economics , Vaccination/veterinaryABSTRACT
Nine feedlot cattle showed clinical signs consistent with those expected in thromboembolic meningoencephalitis. These signs included pyrexia, ataxia, posterior paresis, paralysis and coma. Brown necrotic foci with haemorrhagic borders were observed in the brains of three animals that had died. In these foci vasculitis, thrombosis, infarction and neutrophil infiltration were observed during microscopical examination. Haemophilus somnus was isolated in pure culture from the brains.
