I think season 5 of heartland is on Netflix now and you can find season 6 on YouTube , though poor quality. I searched forever for season 7 and found it but the website took forever to load every 30 seconds so one episode became and hour and a half long. Good luck with your search lol heartland is the most amazing show ever. Wish they would allow us non Canadians to watch more of it :(
It was my understanding all animals used in the show are leased, then go back to the owners when no longer needed. A friend of mine in Alberta was a wrangler for movie companies and it was his job to locate the right animals and work out an arrangement with the owners.