The horse's owner, who was identified only as Budi, said the violent attack, which occurred while the unidentified man was unloading a cart being pulled by the horse, did not come as a major surprise, Jakarta News.Net reported.
"He even attacks chickens if they disturb him when he is eating. That's why I and my family are always careful whenever we are near him," Budi said of his horse.
Following Tuesday's attack at a construction site in the province's Bone Bolango district, the man was taken to a hospital for treatment.
The dismembered testicle was found by a bystander and the severed organ was also be sent to the hospital, Indonesia's ANTARA news agency said.
"Luckily the horse did not chew up or swallow his testicle, but spit it onto the pavement," the unidentified individual who located the detached organ told ANTARA.
It was not reported whether the testicle was reattached.