A man facing 20 bestiality charges allegedly had hundreds of videos of the offensive material.
NSW Detective Superintendent Jane Doherty said the 38-year-old's online presence indicated there was a lot more of the material than police first thought.
"We have viewed in excess of 500 videos at this point and that is just on initial review," Det Doherty said on Wednesday.
"What we have reviewed so far shows that it has been going on for a number of years - we don't have an exact date yet."
The man from the NSW mid-north coast identified online under the pseudonym 'Beast Boy' and allegedly shared bestiality material using encrypted messaging apps.
The material shows the man sexually abusing a variety of animals including dogs, sheep, goats, chickens and a dead kangaroo.
Police say the man was motivated by his desire for sexual gratification as well financial advantage.
"From the conversations he has had, he is very much gratified through his actions," Det Doherty said.
The man faces charges including bestiality, producing bestiality material and disseminating bestiality material, with more charges expected to be laid.
A jack russell terrier cross also was found at the property in Moorland about 30km north of Taree on the NSW mid-north coast on Monday when police arrested him.
The RSCPA say the female dog underwent an examination on Monday and has been named 'Lucky' while in protective custody.
"We can confirm she is safe and doing well," RSPCA Acting Inspector Lachlan King said.
The offending has prompted calls from the Animal Justice Party, for a federal ban on possessing, producing and disseminating bestiality material.
Only in WA, Tasmania and NSW is it illegal.
Animal Justice Party NSW MP Emma Hurst says the crime is heinous and "happening more than people realise".
"This is why we really need this to be a crackdown federally," she told AAP.
"We don't want someone being found guilty in NSW move across the border to another state where they can obtain an animal and continue their offending."
