castration

Examples from literature

At home he castrated one hundred nobly born Roman citizens, though none of us knew of it until after he was dead. 
I may add that it is much better to castrate pigs or hogs when their stomach and intestines are empty, and it is always good practice to feed laxative and easily digested foods sparingly after this operation. 
It has been said that the castrated dog is more attached and faithful to his master than he who has not been deprived of his genital powers: this, however, is to be much doubted. 
They also castrate cattle. 
They do not castrate bullocks. 

castrate | American Dictionary

castrate
verb[ T ]
us/ˈkæs·treɪt/
biology
to remove the testicles (= organs that produce sperm) of a male animal