I think colic can be difficult to diagnose because the symptoms can vary and sometimes mimic other conditions. If not diagnosed quickly and correctly, it could lead to complications like intestinal blockage or rupture, which can be life-threatening for the horse.
As for veterinarians, treating small animals and large mammals can have differences in terms of anatomy, medication dosages, and handling techniques. The area that could be most challenging would depend on the veterinarian's expertise and experience.
Regarding diseases like mad cow disease, it's important to take appropriate measures to prevent the spread of the disease. Killing the entire herd may not always be necessary, as targeted testing, quarantine, and culling of affected animals can be effective in controlling the disease. Each situation should be assessed individually to determine the most appropriate course of action.