Vasectomizing a male, be they ferret, human or other beast, should only
have an effect on their ablity to reproduce.  It should not have any effect
on their behavior (well, they might walk funny for a couple of days...).
In a vasectomy, the vas defrerens,(the tubes that carry the sperm out) are
severed or tied off.  Once any sperm remaining on the way are 'cleared'
thru ejaculation (or die of old age, but I don't know how long that would
be), the animal is rendered effectively sterile (that's sperm-free, not
germ-free :-) ).
 
>So is this just a tube tie?
Yep.
 
Since the rest of the reproductive tract is left as is, there are no changes
in hormone levels, and therefore no change in behavior.  In ferrets, the
purpose of vasectomizing a male would be to produce a male capable of mating
unsucessfully with an intact female, taking her out of heat by inducing
ovulation, but without getting her pregnant.
 
In contrast, castration would involve removal of the testicles and
epididymis, decreasing testosterone levels and thus reducing aggressive
behaviors.  (In farm animals such as sheep, a 'closed' castration (aka
emasculation) is frequently done-the blood vessels to the testicles are
crushed with a clamp, or closed off with special elastic bands.  It takes
longer to be effective than an 'open' castration, ( which is the physical
removal of the testicles via surgery), and sometimes doesn't work, but it's
faster and cheaper.) With either type of castration, the decrease in
agressive behavior would take awhile though, as the hormone levels have to
decrease over a period of time.  A castrated male would be both sterile and
unable to mate.
 
>If so do they vasectomize only older hobs vs the of castrating young kits?
 
Doing one or the other isn't age related; it depends what you want the end
result to be; a calmer male, or a sterile one.  But males that are castrated
while immature won't develop secondary sex characteristics, eg, might not
grow to full size/muscle mass..
[Posted in FML issue 1892]