A stochastic partial-budget analysis of an experimental Pasteurella haemolytica feedlot vaccine trial

A field trial compared a modified Pasteurella haemolytica biotype A serotyp e 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 vac cine groups of 1241 and 1240 head, respectively, and fed in groups of appro ximately 200 head. Morbidity and mortality were monitored until the animals were marketed, Details of pleuritis and pneumonia at veterinary meat inspe ction were recorded for 409 test-vaccinated and 424 control-vaccinated catt le. An increase in morbidity but not mortality risk of respiratory disease was shown between test (13.8% morbidity) and control (11.4% morbidity) grou ps. Cattle with a processing weight <245 kg were 1.4 times more likely to d evelop respiratory diseases than cattle with a processing weight greater th an or equal to 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 v ariables was done to obtain the distribution of possible financial outcomes if the test vaccine were used. Impact (sensitivity) analyses indicated tha t median weight of carcass cut away had the greatest impact on the profit m argin. The partial farm budget highlighted the importance of reducing sub-c linical lesions in a feedlot. (C) 2000 Elsevier Science B.V. All rights res erved.