The older term for the ductus deferens is vas deferens (from L. vasa, a vessel, and L. deferens, present participle of defero, to carry away). Hence the common name for the surgical operation that severs or ligates this organ before it enters the urethra: "vasectomy." To be up to date with modern terminology we really ought to call this a "deferenectomy."
In humans vasectomies are done for purposes of sterilization. They aren't done too often in animals, as the cost and trouble is substantially the same as a straight-out castration; and also, it doesn't confer the benefits of castration, since the testes (and the testosterone source) are left untouched. A vasectomized dog will show the same aggressive behavior and tendency to roam and mate as an untouched one, even though he's "shooting blanks," so to speak. Nevertheless, I dare say that if you asked the dog what he preferred, he'd take the first option.
Lab Exercise List