Sudan was being treated for age-related complications that had affected his muscles and bones and also gave him extensive skin wounds.
The rhino had spent two weeks in late February and early March lying in his pen due to discomfort from a deep wound on his right hind leg.
Sudan had previously lived at the Dver Kralove Zoo in the Czech Republic before being transported to Ol Pejeta Conservancy, about 250 km (155 miles) north of Nairobi, where he lived with the last two females of the same species, 27-year old Najin and 17-year old Fatu.
After all attempts at getting him to mate naturally failed, conservationists last year put Sudan on dating app Tinder, hoping to raise enough money to pay for a $9 million fertility treatment.