It is highly likely that the keyword you provided corresponds to a outside standard distribution channels. Alternatively, it may be a typo for another entry in Rocco Siffredi’s vast filmography (e.g., Rocco's Animal Trainer series, which exists with different numerical entries).
This article investigates the mismatch, explores the actual series progression, and offers the most comprehensive guide to what a hypothetical Animal Trainer 20 would look like, assuming the "Sifferdi" spelling is a simple typo for Rocco Siffredi. To understand why Volume 20 is elusive, we must first establish what does exist. Rocco Siffredi produced the Animal Trainer series primarily through his own studio, Rocco Siffredi Produzioni (later distributed by Evil Angel, Marc Dorcel, and others). Animal Trainer 20 - Rocco Sifferdi -
However, after conducting a thorough search across verified databases, professional film archives (including the official Rocco Siffredi production catalogs), and mainstream entertainment records, (note the spelling discrepancy: Siffredi vs. Sifferdi) could be found. It is highly likely that the keyword you