As in anything else, there are several important things to look for in an injury like this, let me list a few shall we?
Feel for the following:
feel for pulse in the lower extremity, to be sure blood is still properly circulating, if you cannot feel around for a pulse, at least feel the temp. of the leg, if it matches the approx. temp of any of the others, it should be ok.
feel for any broken bones, this should be fairly easy to notice if broken completely, as you may feel the bone ends, or jagged edges within the muscles. manipulate the leg in several postitions, if it swings freely, and you can move it into an unnatural position with little or no resistance, it may be broken.
If broken, you must decide between, euthanasia, home repair, or the best, vet call.
if NOT broken, it very likely can still have severe ligament, and or muscle damage, control swelling with banamine, or if you are a newbee, which i suspect and don't have such meds on hand, then some ice, and or aspirin, yes human asprin, but ONLY if there is NO bleeding internally, otherwise aspirin will cause the blood NOT to clot so easily, and the swelling will get worse.
Isolate calf either with momma only or if bottle baby then by itself or with another of his own age, weight, etc. for companionship.
As swelling goes down, begin some physical therapy...yes. it is a must to prevent that leg from atrophy..
Good luck. :cboy: Medic out!