Serial evaluation of physiologic, pathological, and behavioral changes related to disease progression of experimentally induced Mannheimia haemolytica pneumonia in postweaned calves.
OBJECTIVE
To determine the usefulness of physiologic, behavioral, and pathological changes as objective indicators of early respiratory disease in calves with Mannheimia haemolytica pneumonia.


METHODS
14 crossbred beef steers.


METHODS
Disease was experimentally induced in healthy calves through endoscopic pulmonary inoculation of M haemolytica. Calves were necropsied on days 1, 2, 3, 5, 7, and 9 after inoculation. Physical examination variables (rectal temperature, heart rate, and respiration characteristics), clinical illness score, and degree of activity were assessed 3 times daily beginning 4 days prior to inoculation and continuing throughout the study. Twice before inoculation and on days 1, 2, 3, 5, 7, and 9, arterial blood gas measurements, serum biochemical analyses, and CBCs were performed. Pedometers and accelerometers were used to monitor cattle behavior and activity throughout the trial.


RESULTS
All calves became clinically ill after inoculation and had gross and histopathologic signs of bronchopneumonia. No variable was a reliable indicator of disease progression as judged by percentage of pulmonary involvement. However, activity as measured by total steps taken in a 24-hour period was lower after versus before disease induction.


CONCLUSIONS
This single-pathogen challenge model successfully yielded clinical signs and pathological effects consistent with naturally acquired respiratory disease. Routine laboratory variables and subjective measures were not reliable indicators of lung involvement or the progression of pneumonia. However, activity, objectively measured with pedometers and accelerometers, appeared to be a promising indicator for early recognition of bovine respiratory disease.
Hanzlicek
Gregg A
GA
Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA.
White
Brad J
BJ
Mosier
Derek
D
Renter
David G
DG
Anderson
David E
DE
D000818:Animals; D001772:Blood Cell Count / Q000662:veterinary; D001784:Blood Gas Analysis / Q000662:veterinary; D001831:Body Temperature; D002417:Cattle; D002418:Cattle Diseases / Q000097:blood / Q000473:pathology / Q000503:physiopathology* / Q000523:psychology; D004906:Erythrocyte Count / Q000662:veterinary; D005065:Euthanasia; D006339:Heart Rate; D016018:Least-Squares Analysis; D007958:Leukocyte Count / Q000662:veterinary; D018655:Lymphocyte Count / Q000662:veterinary; D016978:Mannheimia haemolytica / Q000145:classification / Q000472:pathogenicity*; D048089:Pneumonia of Calves, Enzootic / Q000097:blood / Q000473:pathology / Q000503:physiopathology* / Q000523:psychology; D012703:Serotyping; D014886:Weaning