NAVLE® Question of the day

A herd of 25 Holstein heifers present with fever of 104-106°F (40-41.1°C) [N=100-102.5°F, 37.8-39.7°C], lethargy, and purulent nasal discharge.

They also have loud, harsh coughs.

Physical exam reveals crackles over the trachea, but not the lungs.

Fibrinonecrotic plaques are randomly dispersed over the nasal and ocular mucosa, but there are no oral ulcers.

Urine and feces appear normal.

Several affected heifers have an arched back and are straining because of a fibrinonecrotic vaginitis.

Which choice is the most important step to take next to evaluate and prevent this problem in the future? 

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