I would be hesitant to geld if you have very cold weather because I am a firm believer in cold hosing after the procedure. We have done early spring gelding, still a bit chilly, but not below 40F night or day for a week or so. Body is a bit weakened with gelding, open to easier chilling, so why tempt things? Up between his hind legs is a “hot spot” on his body, one of the first places to apply cold water to cool an equine when they overheat! So in cold weather it could easily chill him when his body is stressed, has weakened resistance.
Donkey is different than horse anyway, so watch his drug of choice for sedation. They often need LOTS more than expected. Even safer is tying up a leg during the process to KNOW he can’t cow kick the Vet. They can stroke from muzzle WAYYY out past his rump faster than you can blink. Be safe! Local Vet thought he had BLM donkeys sedated for hoof trimming but Farrier said they were not sedated enough, watching him too hard. Vet laughed, called him a baby, went to pick up a hoof when donkey kicked and gave Vet a new hair part! Vet DID give another shot before heading to ER for stitches with the BO driving. Farrier got donkeys trimmed easily, they did not care anymore after that second shot.
If you can, walk him 3 times a day. More effort on your part, but better for him moving to drain. Time the walks, 30 minutes each session if possible, and keep moving the whole time. Actually just walking is fine, I would time the 30 minutes each session to KNOW he got exercised enough. With colts we can free lunge them walk and gentle trot to get in the time, but I never saw a mule or donkey cooperate with lunging. You do NOT want him running wildly in a round pen situation trying to force his exercise. Leading him is probably the easiest way to exercise him. You also get in “together time” helping him know you better! I do this about 7 days, expecting reduced drainage after the 4th-5th day. Keep any crusty stuff, bloody drips washed away to prevent hair loss. Bigger incisions drain better, take longer to close, so keep checking him for infection.
We have had very good healing, no infections or swelling with this exercise program on our young horses. You do not want to need the Vet making a second visit after gelding is d9ne. Best to get Tetanus, other shots done well before gelding time, to give donkey extra protection with immunity.
It sounds like he will be a nice guy with time, and being gelded will make his life easier anyplace he goes. Too bad he is so beat up, ear nicks and damage may get covered with fuzzy hair in time. Just be very careful, scared animals can act badly, don’t need you getting hurt!