The beast probably swoops down, clutches a cow and rises back in the air to feed somewhere quiet. The hunting range of the dragon is likely to be largish.
You could set up a network of spotters charged with locating the dragon and predicting where it will feed.
The whole area should be freed from large cattle except a few bait ones, grazing in range of a camouflaged observer tasked with igniting a fuse. Then, those cows are equipped with a dynamite vest.
Otherwise, same setup, but with camouflaged Gatling guns or cannons.
There are some substances that might react at above 80 degrees Celsius and be used to permanently equip cattle with exploding vests, but I'm not sure how they'd behave over a long period. Dynamite itself would "sweat" and become unstable.
If the dragon's sight is not too good (a winged predator's probably is very good), fake cows could be disseminated in the countryside and used to bait traps, which would be safer and much less expensive that manning the whole hunting territory with camouflaged Gatling wagons or dynamite-laden cattle. The dragon is likely to need a sizable runway to achieve liftoff, so disrupting the attack run and making it crash in the ground could be enough to immobilize it for long enough to bring guns to the place. Having a wooden cow shoot harpoons or giant bear-traps could do the trick.
There is another alternative which might hurt people's sensibilities.
Assuming the body temperature of the beast is that much higher, it could also be possible to implant cows with a device that I read was used by some Arctic tribes to kill large predators (wolves and bears). A thin, flexible, sharpened sliver of bone (but for us, pointy spring steel with razor borders will do) is compressed inside a ball small enough that it will be likely swallowed whole, made of something that will melt at the target's body temperature but is hard enough at ambient temperature. The original device, called tukmikigiak or possibly mikigiak 1, used lard (ambient temperature being below freezing); we could perhaps use some tar concoction. Once the dragon has swallowed one (or more) devices, the steel blade will uncoil in its stomach or intestine and kill it.
A more humane way, and simpler at that, would be to use smaller balls filled with poison. Assuming we do have a poison that will kill a dragon.
(1) I was led to believe that this device is Sami in origin, but I've discovered that the word used seems to belong to the Inuttitut people.