A male sterilization is called a vasectomy.
The operation is normally done in the physician’s office and takes no more than 20 minutes. The doctor makes two small incisions in the scrotum to provide access to the seminal ducts, which carry sperm from the testicles to the penis. The seminal ducts are severed and sealed. A new method is the no-scalpel vasectomy, substituting a small puncture for the incision.
After a vasectomy the guy still ejaculates as usual, but there are no sperm cells in his semen. The sperm cells remain in the testicles and are absorbed by the blood.
It can take several months before all sperm cells have been cleared from the semen. So the first few months you have to use birth control.
The ejaculate of guys who had a vasectomy doesn’t look any different from that of other guys. That’s because sperm cells only make up 1-3% of the ejaculate. Most of it is fluid from the prostate, thin and milkfish white, and the seminal vesicles, yellow and lumpy. You can only notice there are no sperm cells when you look at the semen under a microscope.