From my experience, generally we use the word related to the kind of animal, i.e. "picuraru", "craparu", "vaccaru", etc.. "Pasturi" is less common. I would say it is ok to use "picuraru" for someone who tends both sheeps and goats, and according to the Sicilian wikipedia, it can also assume a broader meaning (https://scn.wikipedia.org/wiki/Picuraru).

As for the grammar, "pastura" is the plural of "pasturi", it belongs to the kind of masculine names that forms their plural like the neuter in Latin, by changing their ending in -a (the same does "picuraru", its plural is "picurara"). Like "u cannolo"/"i cannola" or "u vrazzu/i vrazza" (the arm/the arms).

A folklore note: I have just learned that in Sicilian the firefly is called "cannila ri picuraru" ("shepherd's candle").

https://www.youtube.com/watch?v=O-HsW142T5g ;   - this is very good

I searched and found that the singer Alessia Tondo has some other good videos on youtube eg https://www.youtube.com/watch?v=9ISq-6D2IvQ

Good songs, I have many of these through Spotify, first searching for Sicilian then following up on the artists and their albums and related artists. Finding the lyrics has been harder so those links are useful.

The incredible Anna Magnani sings Ciuri, ciuri 

<a href="https://youtu.be/AS8QMa8yIrc">https://youtu.be/AS8QMa8yIrc</a>;