You might be missing _ before udp.
Try like: $ host -t SRV _kerberos._udp.samdom.example.com.
_kerberos._udp.samdom.example.com has SRV record 0 100 88 dc1.samdom.example.com.
I found that, without knowing anything about this, using the basic 'soft skill'
of web-searching: "host -t srv" AD
As an example of my 'soft skill', I didn't know what the underscore does.
So, I web-searched: "host -t srv" ad underscore needed
and found:
http://www.rjsystems.nl/en/2100-dns-...y-kerberos.php
Do you now see how useful web-searching can be?
You can also search: "soft skills" for IT|ICT
and spend considerable time studying 'soft skills'.
Best wishes.