Answer:
The subordinate clause is "that my neighbor raises".
Step-by-step explanation:
A subordinate clause, even though containing a subject and a verb, does not express a complete thought on its own. It dependes on the main clause to make sense.
In the case we are studying here, the subordinate clause "that my neighbor raises" only makes sense when attached to "The guinea hens ... are better than watchdogs." In addition, we can say that "that my neighbor raises" is a restrictive subordinate clause. It does not come between commas and it works as an adjective, modifying a noun. In this structure, the plural noun "hens" is being modified by "that my neighbor raises".