Ours are all done standing at the Vet Clinic. All the older colts, older stallions. One Dr situation, they don’t have a table to lay them on. Vet is very experienced, we have not had any problems wit hroses gelder standing. Horse stays a day or two under supervision at the Clinic, they keep horse exercised to keep incision open, draining, then we bring him home. We gently exercise him at least twice daily for 20 minutes to keep things draining, carefully wash off any dry blood or serum on his legs too. Don’t want to knock off any edge scabbing of the incision, but don’t want drying drainage taking off the hair either. We have had no swelling or infection problems.
It will take longer for older, bigger horse to heal than yearlings for example. That is OK, they make a bigger incision on older stallion to get things out, so it takes longer to close. One of ours was almost 4 weeks closing, still seeing a drip of blood now and then . When I asked the Vet about it, he said horse had record sized testicles, biggest Vet had ever seen, including draft horses he had gelded!! Of course such a big incision will take longer to close, very normal. Just keep horse gently exercised and gently clean away any drainage , everything will be fine. Vet was right, horse healed up fine.