Perra pastor belga
 

What is correct or more in use?

Perra pastor belga
Perra pastora belga :?:

I was going to say the first is more used.

Google confirms it is in the Internet:

Perra pastor belga: 225,000 results.
Perra pastora belga: 6,950 results.

Regarding the correctness, just speculating, the use of "pastora" may be related to the politically correct language. I don't know.

Pastor for sure

Don José, you confirmed what I suspected.

I'm not certain, but I think that the term "pastor belga" as the name of a breed of dog is perceived by many people as a noun being used as an attribute of another noun (in this case, "perra"). From what I can find out, more often than not nouns used this way are NOT changed to agree in gender and number with the nouns that they modify, in the same manner as many terms for specific colors such as "malva" and "marrón".

Hang on - we had the discussion only about a week ago with niña prodigio

Thank you to you all!
¡Sois unos foreros fenomenales!